Authors: Yang Zhang (Caltech), Paul M. Bellan (Caltech)

Solar corona loops consist of interwoven braided magnetic strands as observed by the Hi-C Imager [1] and in a new Caltech lab experiment [2]. Braiding and strand-strand reconnection [3] are likely fundamental to loop dynamics. No braided MHD equilibrium model has been reported to our knowledge but would be vital to describe loop evolution. A possible equilibrium is conjectured to be helically symmetric with all strands either having the same Jz polarity or having alternating Jz polarity.  Since actual solar corona loops are expected to have net current flowing between footpoints, the ideal strands should all have the same Jz polarity. We obtain the exact helically braided plasma equilibrium with the same Jz polarity from a Green’s function based, multiple wrapped helical wire model. This equilibrium successfully explains the observed braided structure of the Double Helix Nebula [4].

[1] J. W. Cirtain et al, Nature  493, 501 (2013)

[2] Y. Zhang et al, Nature Astronomy 1-7 (2023)

[3] E. N. Parker, ApJ 174, 499 (1972)

[4] M. Morris et al, Nature 440, 308–310 (2006)