Correction to “A statistical study of the propagation characteristics of whistler waves observed by Cluster”

Abstract

, 2011), the incorrect reference frame (i.e., ISR2) was used to analyze the data. In Figure 2, a statistical analysis of the distribution of wave-normal angles as a function of latitude was presented. The results were obtained using data from the STAFF-SA instrument from the Cluster Active Archive (CAA), by assuming that the data was in the ISR2 coordinate system as written in the data description [Cornilleau-Wehrlin et al., 1997; Cornilleau-Wehrlin and STAFF Team, 2011]. Unfortunately , recently it became evident that the true reference frame system of STAFF-SA data in the CAA is the SR2 (Spin Reference 2) coordinate system, which differs from the ISR2 (inverted SR2) by the inverted signs of the Y and Z axes. We have re-analyzed all of the data in the correct reference frame (i.e., SR2). The results of the new analysis are presented in Figure 1. In the present correction we describe the newly-obtained results and discuss how they impact the discussion in our original paper. [2] Identification of the error only recently became possible when the data of the STAFF-SC instrument in the burst mode, namely, waveforms with a sampling rate of 450 samples per second (that were obtained on January 26, 2001) became available in the CAA. Making use of this data, we performed cross-calibration tests between the STAFF-SC waveforms and the STAFF-SA spectrum matrices. For the comparison, we used observations from a whistler wave that had a frequency of 100 Hz (0.15 of the local f ce). For both STAFF-CA and STAFF-SA we determined that the wave had a circular polarization. The wave-normals determined from the STAFF-SA and STAFF-SC had different signs for the Y and Z components. The vector rotation with respect to the background magnetic field was right-handed from the STAFF-SC (as expected for whistler waves), but left-handed from the STAFF-SA. Since the coordinate system of the STAFF-SC has been verified using FGM data, the results unambiguously demonstrate that the true coordinate system of the STAFF-SA data in the CAA is SR2, not ISR2. The STAFF team, after verification , has confirmed that STAFF Spectral Matrix (SM) and Power Spectral Density (PSD) data at CAA are in SR2 reference frame and not in ISR2 as previously written by mistake (N. Cornilleau-Wehrlin, personal communication, 2012). The CAA documentation has now been modified accordingly by the STAFF team. [3] The corrected probability distribution functions (PDF) of the whistler wave-normal direction q (relative to the background B