Magnetic Footpoint Diffusion at the Sun and Its Relation to the Heliospheric Magnetic Field

The heliospheric magnetic field configuration is largely determined in the solar atmosphere. The interplanetary magnetic field is therefore intimately linked with the coronal structure and evolution during the solar cycle. We summarize recent experimental results from active satellite experiments on Ulysses and the Advanced Composition Explorer (ACE). These results provide constraints on the sources of the solar wind and also the magnetic structure of the heliosphere and the corona. These results suggest the relevance of reconnection processes and differential rotation effects close to the Sun. This leads to large perturbations from a standard Archimedean spiral configuration which cannot be successfully modeled using coronal models which assume a potential magnetic field.

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Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

2000 ◽

Vol 179 ◽

pp. 263-264

Author(s):

K. Sundara Raman ◽

K. B. Ramesh ◽

R. Selvendran ◽

P. S. M. Aleem ◽

K. M. Hiremath

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Flux ◽

Ultra Violet ◽

Active Regions ◽

Morphological Properties ◽

Energy Storage And Conversion ◽

The Sun ◽

X Rays ◽

The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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Polar Magnetic Field Reversals of the Sun in Maunder Minimum

International Astronomical Union Colloquium ◽

10.1017/s0252921100064472 ◽

2000 ◽

Vol 179 ◽

pp. 193-196

Author(s):

V. I. Makarov ◽

A. G. Tlatov

Keyword(s):

Magnetic Field ◽

Maunder Minimum ◽

The Sun ◽

Annual Rings ◽

Field Reversal ◽

Polar Magnetic Field ◽

Pine Trees ◽

Using Data ◽

Magnetic Field Reversal

AbstractA possible scenario of polar magnetic field reversal of the Sun during the Maunder Minimum (1645–1715) is discussed using data of magnetic field reversals of the Sun for 1880–1991 and the14Ccontent variations in the bi-annual rings of the pine-trees in 1600–1730 yrs.

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Erratum: “The north-south asymmetry of the solar and heliospheric magnetic field during activity minima”

Geophysical Research Letters ◽

10.1029/2000gl012889 ◽

2001 ◽

Vol 28 (8) ◽

pp. 1667-1668

Author(s):

S. Bravo

Keyword(s):

Magnetic Field ◽

Heliospheric Magnetic Field ◽

The North ◽

South Asymmetry

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Energetics of magnetic transients in a solar active region plage

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834548 ◽

2019 ◽

Vol 623 ◽

pp. A176 ◽

Cited By ~ 3

Author(s):

L. P. Chitta ◽

A. R. C. Sukarmadji ◽

L. Rouppe van der Voort ◽

H. Peter

Keyword(s):

Magnetic Field ◽

Active Region ◽

Magnetic Flux ◽

Numerical Simulations ◽

Extreme Ultraviolet ◽

Spatial Scales ◽

Coronal Loops ◽

The Sun ◽

Flux Emergence ◽

Transient Events

Context. Densely packed coronal loops are rooted in photospheric plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. Aims. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in the active region plage using high spatial resolution observations and numerical simulations. Methods. We used photospheric Fe I 6173 Å spectropolarimetric observations of a decaying active region obtained from the Swedish 1-m Solar Telescope (SST). These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the extreme-ultraviolet emission maps obtained from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). To obtain better insight into the evolution of extended unidirectional magnetic field patches on the Sun, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. Results. The observations show transient magnetic flux emergence and cancellation events within the extended predominantly unipolar patch on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The numerical simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m−2 through the photosphere. Conclusions. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.

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The Heliospheric Magnetic Field

Space Science Reviews ◽

10.1007/s11214-011-9835-3 ◽

2011 ◽

Vol 176 (1-4) ◽

pp. 177-215 ◽

Cited By ~ 17

Author(s):

André Balogh ◽

Géza Erdõs

Keyword(s):

Magnetic Field ◽

Heliospheric Magnetic Field

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Detection of a change in the North-South ratio of count rates of particles of high-energy cosmic rays during a change in the polarity of the magnetic field of the Sun

JETP Letters ◽

10.1134/s0021364015040086 ◽

2015 ◽

Vol 101 (4) ◽

pp. 228-231

Author(s):

A. V. Karelin ◽

O. Adriani ◽

G. C. Barbarino ◽

G. A. Bazilevskaya ◽

R. Bellotti ◽

...

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

High Energy ◽

The Sun ◽

High Energy Cosmic Rays ◽

The North ◽

The Magnetic Field

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Long-term evolution of the heliospheric magnetic field inferred from cosmogenic 44Ti activity in meteorites

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730392 ◽

2018 ◽

Vol 610 ◽

pp. A28 ◽

Cited By ~ 2

Author(s):

S. Mancuso ◽

C. Taricco ◽

P. Colombetti ◽

S. Rubinetti ◽

N. Sinha ◽

...

Keyword(s):

Magnetic Field ◽

Ice Cores ◽

Long Term Evolution ◽

Galactic Cosmic Rays ◽

Sunspot Activity ◽

Cosmogenic Isotopes ◽

Heliospheric Magnetic Field ◽

The Past ◽

Term Evolution

Typical reconstructions of historic heliospheric magnetic field (HMF) BHMF are based on the analysis of the sunspot activity, geomagnetic data or on measurement of cosmogenic isotopes stored in terrestrial reservoirs like trees (14C) and ice cores (10Be). The various reconstructions of BHMF are however discordant both in strength and trend. Cosmogenic isotopes, which are produced by galactic cosmic rays impacting on meteoroids and whose production rate is modulated by the varying HMF convected outward by the solar wind, may offer an alternative tool for the investigation of the HMF in the past centuries. In this work, we aim to evaluate the long-term evolution of BHMF over a period covering the past twenty-two solar cycles by using measurements of the cosmogenic 44Ti activity (τ1∕2 = 59.2 ± 0.6 yr) measured in 20 meteorites which fell between 1766 and 2001. Within the given uncertainties, our result is compatible with a HMF increase from 4.87-0.30+0.24 nT in 1766 to 6.83-0.11+0.13 nT in 2001, thus implying an overall average increment of 1.96-0.35+0.43 nT over 235 years since 1766 reflecting the modern Grand maximum. The BHMF trend thus obtained is then compared with the most recent reconstructions of the near-Earth HMF strength based on geomagnetic, sunspot number, and cosmogenic isotope data.

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