Statistical Properties of Sub‐Ion Magnetic Holes in the Solar Wind at 1 AU

Abstract

Sub-ion magnetic holes are rich in the terrestrial plasma sheet and magnetosheath. Here, we statistically investigate 60 sub-ion magnetic holes in the solar wind at 1 AU using the high-resolution data measured by the Magnetospheric Multiscale mission. We find that they are observed with a duration of 0.1-0.5 s, and the lengths of their cross-section are~0.1-0.6 ion gyroradius. These structures prefer to occur in the slow solar wind with a weak ambient magnetic field strength. They also prefer to occur in the marginally mirror stable or unstable environments. Electron vortices as well as an enhancement of the electron perpendicular temperature and electron fluxes at~90°pitch angle tend to be observed inside some magnetic holes with a large ambient magnetic field strength. By contrast, there are no clearly observational electron vortices as well as the electron fluxes at~90°pitch angle inside some magnetic holes with a weak ambient magnetic strength. The current density with a value of~10-50 nA/m 2 reveals that the corresponding maximum electron velocity is <10 km/s inside some magnetic holes, lower than the level of the observational electron velocity noise, which prevents the detection of the weak electron vortex. We suggest that electron vortices exist inside all the sub-ion magnetic holes in the solar wind. The generation of these sub-ion magnetic holes can be explained by the electron magnetohydrodynamics soliton and the electron vortex magnetic hole.

Structure of Pc 5 Compressional Waves Observed in the Duskside Outer Magnetosphere: MMS Observations

“…Interestingly, the thin wedge‐like shape cross section is quite different from the geometric shape of the mirror mode structures previously reported in the magnetosheath, solar wind, and terrestrial plasma sheet. The magnetic troughs in these mirror waves are generally recognized as magnetic structures with ellipsoidal (e.g., Wang et al., 2020; Zhang et al., 2008) or cylindrical topology (e.g., Huang et al., 2017; Yao et al., 2017). It has also been confirmed that the cross section of small scale magnetic holes is close to a circular shape or has a more complicated shape by some reconstruction methods (e.g., H. Liu et al., 2019; Y. Y. Liu et al., 2020).…”

Statistical properties of kinetic-scale magnetic holes in terrestrial space

“…Train‐like KSMHs were observed in the solar wind, and clear evidence indicated that they were electron mirror mode structures (Yao ST et al, 2019b). The generation, geometry, and particle behaviors of the solar wind KSMHs were further studied by Wang GQ et al (2020b, c, d).…”

High-precision Calibration of the Fluxgate Magnetometer Offset Vector in the Terrestrial Magnetosheath

“…Our method can calculate the zero offset just using one magnetic dip since four OOPs can be obtained from each magnetic dip. Since the IMF strength is generally <10 nT at 1 au (see Wang et al 2020d), the average B M and B N are expected to be small on each side of the magnetic dip in the solar wind. This indicates that just using several magnetic dips might be able to achieve a high accuracy of the zero offset calculated by our method.…”

“…B T is somewhat flat between 01:46:20 and 01:46:24 UT, and the sharp boundaries are shown by the orange and blue regions in Figure 1. The ambient magnetic field strength is ∼ 40 nT, much stronger than that in the solar wind at 1 au (Wang et al 2020d). The black curves in Figure 1(B) are the magnetic field in the LMN coordinate system determined by minimum variance analysis (MVA; Sonnerup & Scheible 1998) using the data in the interval of 01:46:16-01:46:29 UT.…”