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The long-standing problem of how the solar atmosphere is heated has been addressed by many theoretical studies, which have stressed the relevance of two specific mechanisms, involving magnetic reconnection and waves, as well as the necessity of treating the chromosphere and corona together. But a fully consistent model has not yet been constructed and debate continues, in particular about the possibility of coronal plasma being heated by energetic phenomena observed in the chromosphere. Here we report modelling of the heating of the quiet Sun, in which magnetic fields are generated by a subphotospheric fluid dynamo intrinsically connected to granulation. We find that the fields expand into the chromosphere, where plasma is heated at the rate required to match observations (4,500 watts per square metre) by small-scale eruptions that release magnetic energy and drive sonic motions. Some energetic eruptions can even reach heights of 10 million metres above the surface of the Sun, thereby affecting the very low corona. Extending the model by also taking into account the vertical weak network magnetic field allows for the existence of a mechanism able to heat the corona above, while leaving unchanged the physics of chromospheric eruptions. Such a mechanism rests on the eventual dissipation of Alfvén waves generated inside the chromosphere and that carry upwards the required energy flux of 300 watts per square metre. The model shows a topologically complex magnetic field of 160 gauss on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations, chromospheric features (contributing only weakly to the coronal heating) that can be identified with observed spicules and blinkers, and vortices that may be possibly associated with observed solar tornadoes.

The purpose of this study was to report the management and outcome of 11 patients presenting with chronic Achilles tendon (AT) rupture treated by a modified flexor hallucis longus (FHL) transfer. Seven patients presented with a neglected AT rupture, one with a chronic AT rupture associated with Achilles tendinosis and three with an AT re-rupture. AT defect after fibrosis debridement averaged 7.4 cm. In addition to FHL transfer, we performed an augmentation using the two remaining fibrous scar stumps of the ruptured AT. Functional assessment was performed using the AOFAS score and isokinetic evaluation was performed to assess ankle plantarflexion torque deficit. Follow-up averaged 79 months. Functional outcome was excellent with a significant improvement of the AOFAS score at latest follow-up. No re-rupture nor major complication, particularly of wound healing, was observed. All patients presented with a loss of active range of motion of the hallux interphalangeal joint without functional weakness during athletic or daily life activities. Isokinetic testing at 30 degrees/second and 120 degrees/second revealed a significant average decrease of 28 ± 11% and 36 ± 4.1%, respectively, in plantarflexion peak torque. Although strength deficit persisted at latest follow-up, functional improvement was significant without morbidity due to FHL harvesting. For patients with chronic AT rupture with a rupture gap of at least 5 cm, surgical repair using FHL transfer with fibrous AT stump reinforcement achieved excellent outcomes.

We present the first 3D numerical MHD simulations that show that Taylor's relaxation conjecture is not satisfied in some MHD evolution of magnetic configurations encountered in solar physics. We show that magnetic helicity can be slowly injected through the boundary into a magnetic configuration which then evolves into a MHD disruption, with the formation in finite time of a current sheet through which reconnection occurs, leading to a release of magnetic energy. While helicity is well conserved during the process, it is shown that the relaxed state is far from the constant- alpha linear force-free field that would be predicted by Taylor's conjecture.

We present a new approach to the theory of large-scale solar eruptive phenomena such as coronal mass ejections and two-ribbon flares, in which twisted flux tubes play a crucial role. We show that it is possible to create a highly nonlinear three-dimensional force-free configuration consisting of a twisted magnetic flux rope representing the magnetic structure of a prominence (surrounded by an overlaying, almost potential, arcade) and exhibiting an S-shaped structure, as observed in soft X-ray sigmoid structures. We also show that this magnetic configuration cannot stay in equilibrium and that a considerable amount of magnetic energy is released during its disruption. Unlike most previous models, the amount of magnetic energy stored in the configuration prior to its disruption is so large that it may become comparable to the energy of the open field.