We study the effect of the magnetic field line braiding in the solar atmosphere using topological methods. By measuring the topological entropy of the magnetic field line mapping we show that footpoint motions are capable of inducing highly non-trivial braided structures, which has a fundamental effect on the formation of current layers. Those braids can reach further up in the solar atmosphere, through which energy is transported. Depending on the structure of the field close to the photosphere, such energy transport can be very efficient.

1. Magnetic Field Line
Braiding in the Solar Atmosphere
Simon Candelaresi, David Pontin, Gunnar Hornig

2. Magnetic Carpet
Null Point
Separatrix
Footpoint Motions
Questions: How do disturbances travel into the domain?
Reconnection at null point?
Propagation in presence of nulls?
(Priest et al. 2002)
2

3. E3 Experiments
Full resistive MHD simulations with the PencilCode.
Initially homogeneous field, E3 type of boundary driving.
Braid propagates into domain.
3
Blinking Vortex
Footpoint Driving

4. 4
E3 Experiments
(Yeates et al. 2010)
Controlled change of field line connectivity can be
achieved through footpoint motions.
Field Line Mapping
vs.

5. Null Points
Footpoint motion can alter the field line topology.
5
Null pair creation/annihilation.

6. 6
Energy Propagation
Homogeneous Magnetic Carpet
Topology efficiently inhibits energy propagation.
After change of topology → efficient energy transport.

7. 7
Polarity Mixing
White:
Grey:
Black:
Magnetic field polarities are efficiently
mixed through footpoint motions.

8. Conclusions
● Braiding through photospheric footpoint motion.
● Null point disruption through boundary motions.
● Energy propagation inhibited due to carpet structure.
● Efficient energy transport into corona after topology change.
● Polarity mixing on the photosphere.
simon.candelaresi@gmail.com