The Kinetic Wave Modes generating the Ion-Scale Pressure-Balanced Structures Identified in the Solar Wind

The ion-scale pressure-balanced structures were believed to be the kinetic slow mode waves(KSW) before. Recently, it is reported that both the kinetic slow mode waves and the kinetic Alfven waves(KAW) could form the pressure-balanced structures(PBSs) at the ion or sub-ion scale. And the theoretical calculation results show some opposite signatures of the KAW and the KSW, which could be used to discriminate the two. This work aims to certificate that whether the ion-scale PBSs measured in situ are formed by the KAW or KSW. Here we apply the signatures of the KAW and KSW obtained by the theoretical calculation that the KAW and KSW shows the opposite electric field polarity, opposite magnetic helicity and opposite Alfven ratio (in log). The ion-scale PBSs are measured by Cluster in the solar wind. The wavelet transform is used to obtain the electric field polarity, the magnetic helicity and the Alfven ratio distributing in the time-frequency domain. The results show that in a 3-minute long PBSs region the KAW and KSW signatures appeared adjacently around the proton scale. It supports the former theoretical calculation results that both KAW and KSW could generate the ion-scale PBSs. And this work helps to understand the nature of the compressible fluctuation in the solar wind at the ion scale.