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		| Paper: | 
		What can we Learn from Nonlinear Force-Free Extrapolations? | 
	 
	
		| Volume: | 
		397, First Results From Hinode | 
	 
	
		| Page: | 
		75 | 
	 
	
		| Authors: | 
		Régnier, S. | 
	 
	
	
		| Abstract: | 
		Nonlinear force-free extrapolations are used to determine the 3D nature of the coronal magnetic field. The nonlinear force-free fields require knowledge of the vector magnetic field as boundary conditions at the photospheric or chromospheric level. The development of new vector magnetographs such as Hinode/SOT and SDO/HMI will certainly enhance the science that can be done by combining vector field measurements and nonlinear force-free extrapolations. Here, therefore, we summarize our current work on the key properties of a magnetic configuration: geometry, magnetic energy, magnetic helicity, connectivity and magnetic topology. Physical insights deduced from the magnetic configurations are discussed. | 
	 
	
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