Does the variation of solar inter-network horizontal field follow sunspot cycle?

The ubiquitousness of solar inter-network horizontal magnetic field has been revealed by the space-borne observations with high spatial resolution and polarization sensitivity. However, no consensus has been achieved on the origin of the horizontal field among solar physicists. For a better understanding, in this study we analyze the cyclic variation of inter-network horizontal field by using the spectro-polarimeter observations provided by Solar Optical Telescope on board Hinode, covering the interval from 2008 April to 2015 February. The method of wavelength integration is adopted to achieve a high signal-to-noise ratio. It is found that from 2008 to 2015 the inter-network horizontal field does not vary when solar activity increases, and the average flux density of inter-network horizontal field is 87$\pm$1 G, In addition, the imbalance between horizontal and vertical field also keeps invariant within the scope of deviation, i.e., 8.7$\pm$0.5, from the solar minimum to maximum of solar cycle 24. This result confirms that the inter-network horizontal field is independent of sunspot cycle. The revelation favors the idea that a local dynamo is creating and maintaining the solar inter-network horizontal field.

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