Y. H. Ma's research while affiliated with Harbin Institute of Technology and other places

Publications (6)

Article
Theory predicts that the first adiabatic invariant of a charged particle may be violated in a region of highly curved field lines, leading to significant pitch angle scattering for particles whose gyroradius are comparable to the radius of the magnetic field line curvature. This scattering generates more isotropic particle distribution functions, w...
Article
Unambiguous knowledge of magnetic field structure and the electric current distribution is critical for understanding the origin, evolution and related dynamic properties of magnetic flux ropes (MFRs). In this paper, a survey of 13 MFRs in the Earth's magnetotail are conducted by Cluster multi-point analysis, so that their force-free feature, i.e.,...
Article
Full-text available
The fine magnetic field structure of two successive plasmoids previously reported is investigated by magnetic rotation analysis using four Cluster satellite data. Between these two plasmoids, opposite trends of curvature radius (Rc) variations of the magnetic field lines from the boundary to the inner part are found. The different variations of Rc...
Article
Full-text available
1] We present a generalized multipoint analysis of physical quantities, such as magnetic field and plasma flow, based on spatial gradient properties, where the multipoint data may be taken by irregular (distorted) configurations of any number of spacecraft. The methodology is modified from a previous, fully 3-D gradient analysis technique, designed...
Article
This paper investigates the structure of the magnetic field near the magnetopause (MP) by analyzing the multiple-point magnetic measurements from the Cluster mission. In this paper, the spatial distribution of the curvature radius of the MP surface at the noon-midnight meridian and for situations with moderate dynamical pressure of solar wind is im...

Citations

... In contrast, our simulations show that even large pitch angle particles would experience a transition to chaos in a dipole field with a short length scale. Furthermore, our results are consistent with Cluster measurements that showed depletion of the particle pitch angle distribution for similar ɛ values near magnetic reconnection topology in Earth's magnetosphere ( Zhang et al., 2016 ). ...
... In spacecraft observations, flux ropes are often identified from bipolar variations in one magnetic field component and enhancement of magnetic strength at the center. There are various observations of flux ropes in the magnetosphere (e.g., Khurana et al. 1995;Slavin 2003;Yang et al. 2014;Sun et al. 2019;Poh et al. 2019), boundary of magnetosphere (e.g., Rijnbeek et al. 1984;Kawano & Russell 1997;Fear et al. 2008Fear et al. , 2009Akhavan-Tafti et al. 2018;Hwang et al. 2018;Yao et al. 2020), and solar wind (e.g., Zheng & Hu 2018;BlancoCano et al. 2019;Bai et al. 2020). Flux ropes are also observed in magnetospheres of Mercury (Zhong et al. 2020a), Mars (Briggs et al. 2011), Jupiter (Sarkango et al. 2021), andSaturn (Jasinski et al. 2016). ...
... Such analysis uncovered the true 3-D topological structure of the magnetic field in geomagnetosphere for the first time. As well as the regions mentioned above, the method has been applied to the magnetotail current sheet (Shen et al., 2008a;2008b;Rong et al., 2011), flux ropes or plasmoids (Zhang et al., 2013;Yang et al., 2014), reconnection regions (Lavraud et al., 2016;Zhang et al., 2016), and the cusp and magnetopause Xiao et al., 2018). These results have advanced our understanding of the magnetosphere. ...
... The 3D structure of the geomagnetic field in and near the cusp was investigated further. For instance, Shen et al. (2011) verified the existence of the cusp funnel via a direct estimate of the local field curvature for the first time and showed a possible indentation of the high-altitude magnetopause (Figure 4), concentrating on the cases of strong magnetic shear across the magnetopause which allows to clearly identify the magnetopause. It has been confirmed that pre-cusp magnetic field lines bend sunward while in the post-cusp region the field lines bend tailward and that the minimum curvature radius of the near-magnetopause field lines is about 2.2 R E in both pre-and post-cusp regions. ...
... Clearly, three of the spacecraft provide one component of J normal to that face of the tetrahedron and for very irregular spacecraft separations the relative alignment of the spacecraft configuration to the local field geometry is important, so that often only one face provides an accurate determination of the J component normal to that face (see also the note in Section 3.3 and the methodology in Shen, Rong, Dunlop, Ma, et al., 2012;Vogt et al., 2009). This partial estimate can still provide useful infor- Dunlop et al., 1988;top left); a configuration of the three THEMIS spacecraft in the ring current (from Yang et al., 2016, top right); a configuration of the three Swarm spacecraft (A, B, C) with adjacent positions (A', C') from a few seconds earlier (lower left), and a schematic showing some of the large-scale magnetospheric currents around the Earth (adapted from Kivelson & Russell, 1995, lower right). ...