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An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station showing eastward or poleward drifting.(5)The stripy DDAs are exclusively observed near the MLN and,most importantly,their alignments are confirmed to be consistent with the direction of ionospheric convection near the MLN.(6)A new auroral form,called throat aurora,is found to be developed from the stripy DDAs.Based on the observational results and previous studies,we proposed our explanations to the DDAs.We suggest that the unstructured DDAs observed in the morning are extensions of the nightside diffuse aurora to the dayside,but that observed in the afternoon are predominantly caused by proton precipitations.The structured DDAs occurred near the MLN are caused by interactions of cold plasma structures,which are supposed to be originated from the ionospheric outflows or plasmaspheric drainage plumes,with hot electrons from the plasma sheet.We suppose that the cold plasma structures for producing the patchy DDAs are in lumpy and are more likely from the plasmaspheric drainage plumes.The cold plasm structure for producing the stripy DDAs should be in wedge-like and are generated by conveying the cold plasmas from lower latitude towards higher latitude with magnetospheric convection,and that for producing the irregular DDAs are resulted from deforming the wedge-like structure by disturbance.The throat aurora is supposed to be projection of a newly-opened flux of reconnection.In addition,we also found that structured DDAs correspond to structured electron precipitations in the ionosphere,which implies that the cold plasma structures in the magnetosphere are magnetically mapped to the ionosphere and act as a duct for producing the structured DDAs.We argue that we have presented some new observational results about DDA in this paper,which will be useful for fully understanding the DDAs.