Toroidal Flux Ropes with Elliptical Cross Sections and Their Magnetic Helicity

0484736 - ASÚ 2018 RIV NL eng J - Journal Article
Vandas, Marek - Romashets, E.
Toroidal Flux Ropes with Elliptical Cross Sections and Their Magnetic Helicity.
Solar Physics. Roč. 292, č. 9 (2017), 129/1-129/23. ISSN 0038-0938. E-ISSN 1573-093X
R&D Projects: GA ČR(CZ) GA14-19376S; GA ČR(CZ) GA17-06065S
Institutional support: RVO:67985815
Keywords : coronal mass ejections * interplanetary * helicity
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 2.580, year: 2017

Axially symmetric constant-alpha force-free magnetic fields in toroidal flux ropes with elliptical cross sections are constructed in order to investigate how their alphas and magnetic helicities depend on parameters of the flux ropes. Magnetic configurations are found numerically using a general solution of a constant-alpha force-free field with an axial symmetry in cylindrical coordinates for a wide range of oblatenesses and aspect ratios. Resulting alphas and magnetic helicities are approximated by polynomial expansions in parameters related to oblateness and aspect ratio. These approximations hold for toroidal as well as cylindrical flux ropes with an accuracy better than or of about 1%. Using these formulae, we calculate relative helicities per unit length of two (probably very oblate) magnetic clouds and show that they are very sensitive to the assumed magnetic cloud shapes (circular versus elliptical cross sections).
Permanent Link: http://hdl.handle.net/11104/0279882