Variations of helioseismic parameters due to magnetic field generated by a flux transport model

AbstractSome key physical processes that impact the evolution of Earth's atmosphere on time-scale from days to millennia, such as the EUV emissions, are determined by the solar magnetic field. However, observations of the solar spectral irradiance are restricted to the last few solar cycles and are subject to large uncertainties. We present a physics-based model to reconstruct short-term solar spectral irradiance (SSI) variability. The coronal magnetic field is estimated to employ the Potential Field Source Surface extrapolation (PFSS) based on observational synoptic charts and magnetic flux transport model. The emission is estimated to employ the CHIANTI atomic database 8.0. The performance of the model is compared to the emission observed by TIMED/SORCE.

Download Full-text

Modelling coronal electron density and temperature profiles based on solar magnetic field observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003799 ◽

2016 ◽

Vol 12 (S328) ◽

pp. 159-161

Author(s):

J. M. Rodríguez Gómez ◽

L. E. Antunes Vieira ◽

A. Dal Lago ◽

J. Palacios ◽

L. A. Balmaceda ◽

...

Keyword(s):

Magnetic Field ◽

Solar Corona ◽

Electron Density ◽

Transport Model ◽

Source Surface ◽

Temperature Profiles ◽

Emission Model ◽

Flux Transport ◽

Field Source ◽

Electron Density And Temperature

AbstractThe density and temperature profiles in the solar corona are complex to describe, the observational diagnostics is not easy. Here we present a physics-based model to reconstruct the evolution of the electron density and temperature in the solar corona based on the configuration of the magnetic field imprinted on the solar surface. The structure of the coronal magnetic field is estimated from Potential Field Source Surface (PFSS) based on magnetic field from both observational synoptic charts and a magnetic flux transport model. We use an emission model based on the ionization equilibrium and coronal abundances from CHIANTI atomic database 8.0. The preliminary results are discussed in details.

Download Full-text

Dipolar and Quadrupolar Magnetic Field Evolution over Solar Cycles 21, 22, and 23

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311017492 ◽

2010 ◽

Vol 6 (S271) ◽

pp. 94-101 ◽

Cited By ~ 1

Author(s):

M. L. DeRosa ◽

A. S. Brun ◽

J. T. Hoeksema

Keyword(s):

Magnetic Field ◽

Spherical Harmonic ◽

Transport Model ◽

Activity Cycle ◽

Surface Flux ◽

Solar Activity Cycle ◽

Solar Photosphere ◽

Solar Cycles ◽

Flux Transport ◽

The Past

AbstractTime series of photospheric magnetic field maps from two observatories, along with data from an evolving surface-flux transport model, are decomposed into their constituent spherical harmonic modes. The evolution of these spherical harmonic spectra reflect the modulation of bipole emergence rates through the solar activity cycle, and the subsequent dispersal, shear, and advection of magnetic flux patterns across the solar photosphere. In this article, we discuss the evolution of the dipolar and quadrupolar modes throughout the past three solar cycles (Cycles 21–23), as well as their relation to the reversal of the polar dipole during each solar maximum, and by extension to aspects of the operation of the global solar dynamo.

Download Full-text

The Sun’s polar magnetic field: datasets, proxies and theoretical issues

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318001345 ◽

2018 ◽

Vol 13 (S340) ◽

pp. 289-292

Author(s):

Arnab Rai Choudhuri

Keyword(s):

Magnetic Field ◽

Transport Model ◽

Sunspot Cycle ◽

Surface Flux ◽

Dynamo Model ◽

Flux Transport ◽

Polar Magnetic Field ◽

Theoretical Issues ◽

Dynamo Process ◽

Good Precursor

AbstractThe polar magnetic field of the Sun is a manifestation of certain aspects of the dynamo process and is a good precursor for predicting a sunspot cycle before its onset. Although actual synoptic measurements of this field exist only from the mid-1970s, it has now been possible to determine its evolution from the beginning of the twentieth century with the help of various proxies. The recently developed 3D kinematic dynamo model can study the build-up of the Sun’s polar magnetic field more realistically than the earlier surface flux transport model.

Download Full-text

How to make the Sun look less like the Sun and more like a star?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003908 ◽

2016 ◽

Vol 12 (S328) ◽

pp. 237-239

Author(s):

A. A. Vidotto

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Vector Fields ◽

Radial Component ◽

Field Vector ◽

Small Scale ◽

General Context ◽

The Sun ◽

Flux Transport ◽

Large Scale Magnetic Field

AbstractSynoptic maps of the vector magnetic field have routinely been made available from stellar observations and recently have started to be obtained for the solar photospheric field. Although solar magnetic maps show a multitude of details, stellar maps are limited to imaging large-scale fields only. In spite of their lower resolution, magnetic field imaging of solar-type stars allow us to put the Sun in a much more general context. However, direct comparison between stellar and solar magnetic maps are hampered by their dramatic differences in resolution. Here, I present the results of a method to filter out the small-scale component of vector fields, in such a way that comparison between solar and stellar (large-scale) magnetic field vector maps can be directly made. This approach extends the technique widely used to decompose the radial component of the solar magnetic field to the azimuthal and meridional components as well, and is entirely consistent with the description adopted in several stellar studies. This method can also be used to confront synoptic maps synthesised in numerical simulations of dynamo and magnetic flux transport studies to those derived from stellar observations.

Download Full-text

Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles

10.5194/egusphere-egu21-3719 ◽

2021 ◽

Author(s):

David Ruffolo ◽

Rohit Chhiber ◽

William H. Matthaeus ◽

Arcadi V. Usmanov ◽

Paisan Tooprakai ◽

...

Keyword(s):

Magnetic Field ◽

Random Walk ◽

Field Line ◽

Large Scale ◽

Transport Model ◽

Source Region ◽

Science Research ◽

Energetic Particles ◽

Solar Energetic Particles ◽

Field Lines

<p>The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles (SEPs) propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20 &#8211; 60 degrees. In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20 degrees. Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165). &#160;MLG acknowledges support from the Parker Solar Probe FIELDS MAG team. &#160;Additional support is acknowledged from the&#160; NASA LWS program&#160; (NNX17AB79G) and the HSR program (80NSSC18K1210 & 80NSSC18K1648).</p>

Download Full-text

Hemispheric injection of magnetic helicity by surface flux transport

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936475 ◽

2019 ◽

Vol 631 ◽

pp. A138 ◽

Cited By ~ 3

Author(s):

G. Hawkes ◽

A. R. Yeates

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Solar Rotation ◽

Surface Flux ◽

Magnetic Helicity ◽

Solar Cycles ◽

Flux Transport ◽

Transport Models ◽

Radial Magnetic Field ◽

Helicity Injection

Aims. We estimate the injection of relative magnetic helicity into the solar atmosphere by surface flux transport over 27 solar cycles (1700–2009). Methods. We determine the radial magnetic field evolution using two separate surface flux transport models: one driven by magnetogram inputs and another by statistical active region insertion guided by the sunspot number record. The injection of relative magnetic helicity is then computed from this radial magnetic field together with the known electric field in the flux transport models. Results. Neglecting flux emergence, solar rotation is the dominant contributor to the helicity injection. At high latitudes, the injection is always negative/positive in the northern/southern hemisphere, while at low latitudes the injection tends to have the opposite sign when integrated over the full solar cycle. The overall helicity injection in a given solar cycle depends on the balance between these two contributions. This net injected helicity correlates well with the end-of-cycle axial dipole moment.

Download Full-text

A Quantitative Study of Magnetic Flux Transport on the Sun

Symposium - International Astronomical Union ◽

10.1017/s0074180900029934 ◽

1983 ◽

Vol 102 ◽

pp. 273-278 ◽

Cited By ~ 2

Author(s):

N.R. Sheeley ◽

J.P. Boris ◽

T.R. Young ◽

C.R. DeVore ◽

K.L. Harvey

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Quantitative Study ◽

Differential Rotation ◽

Meridional Circulation ◽

Diffusion Constant ◽

The Sun ◽

Flux Transport ◽

Field Reversal ◽

Best Fit

A computational model, based on diffusion, differential rotation, and meridional circulation, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, we have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. Our value of 730 ± 250 km2/s is consistent with Leighton's (1964) estimate of 770–1540 km2/s and is significantly larger than Mosher's (1977) estimate of 200–400 km2/s. This suggests that diffusion may be fast enough to account for the observed polar magnetic field reversal without requiring a significant assist from meridional currents.

Download Full-text

Optimization of surface flux transport models for the solar polar magnetic field

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936099 ◽

2019 ◽

Vol 632 ◽

pp. A87 ◽

Cited By ~ 6

Author(s):

K. Petrovay ◽

M. Talafha

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Parameter Space ◽

Large Scale ◽

Surface Flux ◽

Supporting Evidence ◽

Flux Transport ◽

Polar Magnetic Field ◽

Flow Profiles ◽

Magnetic Diffusivity

Context. The choice of free parameters in surface flux transport (SFT) models describing the evolution of the large-scale poloidal magnetic field of the Sun is critical for the correct reproduction of the polar magnetic flux built up during a solar cycle, which is known to be a good predictor of the amplitude of the upcoming cycle. Aims. For an informed choice of parameters it is important to understand the effects of and interplay among the various parameters and to optimize the models for the polar magnetic field. Methods. Here we present the results of a large-scale systematic study of the parameter space in an SFT model where the source term representing the net effect of tilted flux emergence was chosen to represent a typical, average solar cycle as described by observations. Results. Comparing the results with observational constraints on the spatiotemporal variation of the polar magnetic field, as seen in magnetograms for the last four solar cycles, we mark allowed and excluded regions in the 3D parameter space defined by the flow amplitude u0, the magnetic diffusivity η and the decay time scale τ, for three different assumed meridional flow profiles. Conclusions. Without a significant decay term in the SFT equation (i.e., for τ > 10 yr) the global dipole moment reverses too late in the cycle for all flow profiles and parameters, providing independent supporting evidence for the need of a decay term, even in the case of identical cycles. An allowed domain is found to exist for τ values in the 5–10 yr range for all flow profiles considered. Generally higher values of η (500–800 km2 s−1) are preferred though some solutions with lower η are still allowed.

Download Full-text

A theoretical model of torsional oscillations from a flux transport dynamo model

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311015560 ◽

2010 ◽

Vol 6 (S273) ◽

pp. 366-368

Author(s):

Piyali Chatterjee ◽

Sagar Chakraborty ◽

Arnab Rai Choudhuri

Keyword(s):

Magnetic Field ◽

Theoretical Model ◽

Lorentz Force ◽

High Latitude ◽

Torsional Oscillation ◽

Sunspot Cycle ◽

Dynamo Model ◽

Flux Transport ◽

Torsional Oscillations ◽

The Magnetic Field

AbstractAssuming that the torsional oscillation is driven by the Lorentz force of the magnetic field associated with the sunspot cycle, we use a flux transport dynamo to model it and explain its initiation at a high latitude before the beginning of the sunspot cycle.

Download Full-text