POLAR FIELD PUZZLE: SOLUTIONS FROM FLUX-TRANSPORT DYNAMO AND SURFACE-TRANSPORT MODELS

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.

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In Search of the Plastic Accumulation Regions: Finetuning Ocean Surface Transport Models

Fate and Impact of Microplastics in Marine Ecosystems ◽

10.1016/b978-0-12-812271-6.00136-8 ◽

2017 ◽

pp. 139

Author(s):

R. Mcadam ◽

E. Van Sebille

Keyword(s):

Ocean Surface ◽

Transport Models ◽

Surface Transport

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How Good Is the Bipolar Approximation of Active Regions for Surface Flux Transport?

Solar Physics ◽

10.1007/s11207-020-01688-y ◽

2020 ◽

Vol 295 (9) ◽

Cited By ~ 1

Author(s):

Anthony R. Yeates

Keyword(s):

Dipole Moment ◽

Active Region ◽

Transport Model ◽

Active Regions ◽

Surface Flux ◽

Flux Transport ◽

Transport Models ◽

Magnetic Structures ◽

Axial Dipole ◽

Flow Parameters

Abstract We investigate how representing active regions with bipolar magnetic regions (BMRs) affects the end-of-cycle polar field predicted by the surface flux transport model. Our study is based on a new database of BMRs derived from the SDO/HMI active region patch data between 2010 and 2020. An automated code is developed for fitting each active region patch with a BMR, matching both the magnetic flux and axial dipole moment of the region and removing repeat observations of the same region. By comparing the predicted evolution of each of the 1090 BMRs with the predicted evolution of their original active region patches, we show that the bipolar approximation leads to a 24% overestimate of the net axial dipole moment, given the same flow parameters. This is caused by neglecting the more complex multipolar and/or asymmetric magnetic structures of many of the real active regions, and may explain why previous flux transport models had to reduce BMR tilt angles to obtain realistic polar fields. Our BMR database and the Python code to extract it are freely available.

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Solar-cycle precursors and predictions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313002196 ◽

2012 ◽

Vol 8 (S294) ◽

pp. 49-60 ◽

Cited By ~ 1

Author(s):

Jie Jiang

Keyword(s):

Solar Cycle ◽

Polar Field ◽

Magnetic Memory ◽

Flux Transport ◽

Geomagnetic Variations ◽

Magnetic Diffusivity ◽

Time Period ◽

Set Up ◽

Open Flux ◽

Robust Prediction

AbstractThe sunspot number data during the past 400 years indicates that both the profile and the amplitude of the solar cycle have large variations. Some precursors of the solar cycle were identified aiming to predict the solar cycle. The polar field and the geomagnetic index are two precursors which are received the most attention. The geomagnetic variations during the solar minima are potentially caused by the solar polar field by the connection of the solar open flux. The robust prediction skill of the polar field indicates that the memory of the dynamo process is less than 11 yrs based on the frame of the Babcock-Leighton flux transport dynamo. One possible reason to get the short magnetic memory is the high magnetic diffusivity in the convective zone. Our recent studies show that the radial downward pumping is another possible reason. Based upon the mechanism, we well simulate the cycle irregularities during RGO time period. This opens the possibility to set up a standard dynamo based model to predict the solar cycle. In the end, the no correlation between the polar field and the preceding cycle strength due to two nonlinearities involved in the sunspot emergence will be stressed.

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