Issue |
A&A
Volume 581, September 2015
|
|
---|---|---|
Article Number | A6 | |
Number of page(s) | 7 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361/201526654 | |
Published online | 24 August 2015 |
Bipolar solar magnetic fields
Behaviors resulting from a nonlinear force-free equation
1
Zentrum für Astronomie und Astrophysik, Technische Universität
Berlin, Hardenbergstraße
36, 10623
Berlin, Germany
e-mail: robert.c.tautz@gmail.com
2
Institut für Geowissenschaften, Naturwissenschaftliche Fakultät
III, Martin-Luther-Universität Halle, 06099
Halle,
Germany
e-mail: lercheian@yahoo.com
Received:
2
June
2015
Accepted:
15
July
2015
Aims. Understanding magnetic fields in the solar corona is closely related to the complex nature of the often nonlinear differential equations describing such structures. Based on the ansatz of force-free fields, a class of solutions is derived and discussed that allows for axisymmetric bipolar magnetic fields.
Methods. Allowed dipolar solutions for self-similar axisymmetric force-free magnetic fields use the formalism of a Grad-Shafranov equation involving the vector potential. For separable solutions involving poloidal fields decaying radially as r−n, there are no dipolar field structures for the decay index n ≥ 1 .
Results. In the domain n < 1 dipolar field structures are possible in restricted ranges of the angular coordinate θ depending on the value for n. Outside of the restricted domains there are no dipolar solutions, but there can be multipole solutions. The limiting case of the parameter n → 0 has been discussed previously, so that now the full regime 0 ≤ n < ∞ is covered.
Key words: plasmas / magnetic fields / Sun: corona / Sun: magnetic fields / methods: analytical
© ESO, 2015
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.