Correlation properties of magnetosheath magnetic field fluctuations

摘要

The magnetosheath is characterized by a variety of low-frequency fluctuations, buttheir features and sources are different. Taking advantage of multipoint magnetic fieldmeasurements of the Cluster spacecraft, we present a statistical study to reveal propertiesof waves. We compute cross-correlation coefficients of magnetic field strengths asmeasured by pairs of the Cluster spacecraft and determine the correlation length ofmagnetosheath waves. We discuss the relationship between the correlation length andupstream parameters as well as its connection with the wave mode and frequency powerspectrum. In the frequency interval of 0.001-0.125 Hz, we found that the correlationlength of fluctuations increases (1) through intervals of high solar wind speeds, (2) withincreasing interplanetary magnetic field (IMF) strength, (3) if the cross-correlationbetween the IMF and magneto sheath magnetic field is higher, and (4) if the amplitude offluctuations is larger.