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Magnetic helicity is an invariant of ideal magnetohydrodynamics (MHD) that encodes information on the topology of magnetic field lines. It has long been appreciated that magnetic topology is an important constraint for the evolution of…

Solar and Stellar Astrophysics · Physics 2020-09-25 David MacTaggart , Chris Prior

Evidence for the emergence of twisted flux tubes into the solar atmosphere has, so far, come from indirect signatures. In this work, we investigate the topological input of twisted flux tube emergence directly by studying helicity and…

Solar and Stellar Astrophysics · Physics 2020-03-09 David MacTaggart , Chris Prior

Observations of magnetic helicity transportation through the solar photosphere reflect the interaction of turbulent plasma movements and magnetic fields in the solar dynamo process. In this chapter, we have reviewed the research process of…

Solar and Stellar Astrophysics · Physics 2023-11-14 Hongqi Zhang , Shangbin Yang , Haiqing Xu , Xiao Yang , Jie Chen , Jihong Liu

Magnetic fields emerging from the Sun's interior carry information about physical processes of magnetic field generation and transport in the convection zone. Soon after appearance on the solar surface the magnetic flux gets concentrated in…

Solar and Stellar Astrophysics · Physics 2009-11-13 A. G. Kosovichev

The emergence of dipolar magnetic features on the solar surface is an idealization. Most of the magnetic flux emergence occurs in complex multipolar regions. Here, we show that the surface pattern of magnetic structures alone can reveal the…

Solar and Stellar Astrophysics · Physics 2018-12-11 Philippe-A. Bourdin , Axel Brandenburg

Using a 3D non-linear mean-field solar dynamo model, we investigate the magnetic helicity flux and magnetic twist, and tilt parameters of bipolar magnetic regions (BMRs) emerging from the solar convection zone due to the magnetic buoyancy…

Solar and Stellar Astrophysics · Physics 2025-08-04 V. V. Pipin , Shangbin Yang , A. G. Kosovichev

We study the emergence of magnetic flux from the near-surface layers of the solar convection zone into the photosphere. To model magnetic flux emergence, we carried out a set of numerical radiative magnetohydrodynamics simulations. Our…

Astrophysics · Physics 2009-11-13 Mark Chun Ming Cheung , Manfred Schuessler , Fernando Moreno-Insertis

We studied 101 flux emergence events ranging from small ephemeral regions to large emerging flux regions which were observed with Hinode Solar Optical Telescope filtergram. We investigated how the total magnetic flux of the emergence event…

Solar and Stellar Astrophysics · Physics 2015-05-28 Kenichi Otsuji , Reizaburo Kitai , Kiyoshi Ichimoto , Kazunari Shibata

We present a new methodology which can determine magnetic helicity transport by the passage of helical magnetic field lines from sub-photosphere and the shuffling motions of foot-points of preexisting coronal field lines separately. It is…

Solar and Stellar Astrophysics · Physics 2015-06-04 Y. Zhang , R. Kitai , K. Takizawa

Magnetic helicity is a key geometrical parameter to describe the structure and evolution of solar coronal magnetic fields. The accumulation of magnetic helicity is correlated with the non-potential magnetic field energy, which is released…

Solar and Stellar Astrophysics · Physics 2024-12-25 Shangbin Yang , Suo Liu , Jiangtao Su , Yuanyong Deng

Sunspots and active regions observed on the solar surface are widely believed to be manifestations of compact predominantly-toroidal magnetic field structures (``flux tubes") that emerge by magnetic buoyancy from the deeper interior of the…

Solar and Stellar Astrophysics · Physics 2024-06-21 Bhishek Manek , Nicholas Brummell

Field line helicity measures the net linking of magnetic flux with a single magnetic field line. It offers a finer topological description than the usual global magnetic helicity integral, while still being invariant in an ideal evolution…

Solar and Stellar Astrophysics · Physics 2023-11-16 A. R. Yeates , M. A. Berger

Dynamos in the Sun and other bodies tend to produce magnetic fields that possess magnetic helicity of opposite sign at large and small scales, respectively. The build-up of magnetic helicity at small scales provides an important saturation…

Solar and Stellar Astrophysics · Physics 2010-11-30 Piyali Chatterjee , Gustavo Guerrero , Axel Brandenburg

By defining an appropriate field line helicity, we apply the powerful concept of magnetic helicity to the problem of global magnetic field evolution in the Sun's corona. As an ideal-magnetohydrodynamic invariant, the field line helicity is…

Solar and Stellar Astrophysics · Physics 2017-07-05 A. R. Yeates , G. Hornig

Solar flares and coronal mass ejections, the primary space weather disturbances affecting the entire heliosphere and near-Earth environment, mainly emanate from sunspot regions harbouring high degrees of magnetic twist. However, it is not…

Solar and Stellar Astrophysics · Physics 2023-06-01 Shin Toriumi , Hideyuki Hotta , Kanya Kusano

Magnetic helicity quantifies how globally sheared and/or twisted is the magnetic field in a volume. This quantity is believed to play a key role in solar activity due to its conservation property. Helicity is continuously injected into the…

Solar and Stellar Astrophysics · Physics 2013-07-11 K. Dalmasse , E. Pariat , P. Démoulin , G. Aulanier

We present results from numerical modeling of emerging flux regions on the solar surface. The modeling was carried out by means of 3D radiative MHD simulations of the rise of buoyant magnetic flux tubes through the convection zone and into…

Astrophysics · Physics 2009-11-13 M. C. M. Cheung , M. Schuessler , T. D. Tarbell , A. M. Title

Small-scale magnetic flux emergence in the quiet Sun is crucial for maintaining solar magnetic activity. On the smallest scales studied so far, namely within individual granules, two mechanisms have been identified: emergence in tiny…

Solar and Stellar Astrophysics · Physics 2025-03-05 S. M. Díaz-Castillo , C. E. Fischer , F. Moreno-Insertis , S. L. Guglielmino , R. Ishikawa , S. Criscuoli

Flux emergence is crucial for the formation of solar active regions and triggering of various eruptions. However, the detailed mechanisms by which flux emergence drives these eruptions remain unclear and require numerical investigation.…

Solar and Stellar Astrophysics · Physics 2025-06-18 Xiaohong Li , Yuhao Zhou , Rony Keppens

We perform a study of fluid motions and its temporal evolution in and around a small bipolar emerging flux region using observations made by the Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamics Observatory (SDO). We employ…

Solar and Stellar Astrophysics · Physics 2020-06-03 C. R. Sangeetha , Durgesh Tripathi , S. P. Rajaguru
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