程鑫XinCheng新一代信息技术产业南京大学
Study Fields: Solar Physics and Space Science
---Understanding Energetic Eruptions in the Heliosphere and Beyond
Today of The Sun
Visited Scientists、Useful Links、Useful Tools
Papers for new PhD students、Papers on Reconnection
Project 1. Origin and Evolution of Coronal Mass Ejections
Coronal mass ejections (CMEs) and solar flares are the most energetic eruptive phenomena in our solar system and can release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind, probably giving rise to severe space weather effects. The aim of this project is toward understanding the orgin and early evolution of CMEs/flares through multi-wavelength observational perspective. The figure on the right shows a CME observed by the Large Angle and Spectrometric Coronagraph on board the Solar and Heliospheric Observatory. The zoom-in of the flaring region indicated by the white box shows an erupting hot magnetic flux rope (10 million-degree) at 131 angstrom observed by the Atmospheric Imaging Assembly telescope on board the Solar Dynamics Observatory.
Publications:
Cheng, X., Zhang, J., Liu, Y., Ding, M. D, 2011, ApJL 732, L25
Zhang, J., Cheng, X Ding, M. D., 2012 Nature Communications 3, 747 (Featured)
Cheng, X., Zhang, J., Ding, M. D., et al., 2013, ApJ 763, 43
Cheng, X., Ding, M. D., Guo, Y., et al., 2014, ApJ 780, 28
Cheng, X., Ding, M. D., 2016, ApJS 225, 16
Zhou, Z. J. Cheng, X., Liu, L. J., et al. 2019, ApJL, 877, L28
Cheng, X., Zhang, J., Kliem, B., Torok, T., et al. 2020, in review
Code for Kinematic analysis
Project 2. Formation of Magnetic Flux Rope
In the solar corona, due to high conductivity, the plasma is frozen to magnetic field, the configurations and dynamics of magnetic field therefore controll the structures and motion behavior of the plasma. The aim of this project is to address the flux rope formation through investigating 3D structures and thermodynamics of pre-eruptive configurations and different components of CMEs/flares in terms of extrapolation technologies and differential emission measure methods. The figure on the right shows the emission distributions at the different temperature range (3-4 MK and 8-10 MK) and corresponding 3D magnetic structure for a pre-existing flux rope on 2012 July 12.
Publications:
Cheng, X., Zhang, J., Saar, S. H., Ding, M. D., 2012, ApJ 761, 62
Cheng, X., Ding, M. D., Zhang, J., et al. 2014, ApJ 789, 93
Cheng, X., Ding, M. D., Fang, C., 2015, ApJ 804, 82
Liu, L. J., Cheng, X., Wang, Y. M., et al. 2018, ApJL, 867, L5
Liu, L. J., Cheng, X., Wang, Y. M., et al. 2019, ApJ, 884, 45
Code for DEM inversion
Project 3. 3D Features and Evolution of Magnetic Reconnection
Magnetic reconnection, a change of magnetic field connectivity, is a fundamental physical process in the Universe. During solar eruptions, the reconnection, taking place between CMEs and flares, releases magnetic energy explosively to power the CME eruption and the flare emission. Owing to three-dimensionality of erupting structures and magnetic environments, the reconnection will present a 3D evolution process. The aim of this project is to reveal 3D features and evolution of magnetic reconnection during CMEs/flares. The figure on the right displays 3D magnetic field structures during the flux rope eruption, in which the reconnection converts two sheared overlying field lines to a flare loop and a twisted field line that is added to the pre-existing rising flux rope.
Publications:
Cheng, X., Zhang, J., Liu, Y., Ding, M. D, 2011, ApJL 732, L25
Sun, J. Q., Cheng, X., Ding, M. D., et al., 2015, Nature Communications 6, 7598 (Featured)
Cheng, X., Li, Y., Wan, L. F., et al., 2018, ApJ 866, 64 (Press release)
Xing, C., Cheng, X., Qiu, J., et al., 2019, ApJ in press
Project 4. Coronal Shocks and Solar Radio Bursts
As CMEs erupt upward, coronal shocks may form at the front of the CMEs, generaging metric type II radio bursts, a narrow-band radio emission enhancement excited at the local plasma frequency. On the other hand, eletron beams, accelerated in the reconnection region, produce type III radio bursts simultaneously. At present, the questions of how coronal shocks are formed, what properties do they have, and what conditions do they need to generate type II/III radio emissions remain. This project involves various ground-based solar radio observations such as MUSER and space-based missions. The figure on the right represents a coronal shock wave driven by the erupting CME. The outermost bright front indicates the shock front, followed by a bright sheath region.
Publications:
Cheng, X., Zhang, J., Olmedo, O., et al., 2012, ApJL 745, L5Su, W., Cheng, X., Ding, M. D., et al., 2015, ApJ 804, 88Su, W., Cheng, X., Ding, M. D., et al., 2016, ApJ 830, 70Wan, L., Cheng, X., Shi, T., Su, W., Ding, M. D., 2016, ApJ 826, 174
Project 5. Predicting Arrival of Coronal Mass Ejections
After experiencing a propagation phase of 1-3 days, CMEs may arrive at the Earth and take the from of magnetic clounds with the features of rotation of magnetic field, increased solar wind speed, depressed proton temperature, and low plasma beta. Due to the interaction with the magnetosphere and ionosphere, geomagnetic stroms probably take place, seriously impacting on the safety of high-tech activities in outer space, such as disrupting communications, presenting a hazard to astronauts and so on. In this project, the aim is to predict arrival time of CMEs taking advantage of kinematical models and initial parameters. The figure on the right shows a cartoon of a magnetic cloud interacting with the magnetosphere.
Publications:
Shi, T., Wang, Y., Wan, L., Cheng, X., Ding, M., Zhang, J., 2015, ApJ 806, 271
PhD Students:
Zhuofei Li (Project 3)
Chen Xing (Project 2 and 3)
Wei Su (Co-supervisor, Project 4, graduated in 2015, Postdoc in Huazhong University of Science and Technology)
Jianqing Sun (Co-supervisor, Project 3, graduated in 2017, Research Scientist in Philips)
Master Students:
Ziwen Huang (Project 1)
Linfeng Wan (Project 1 and 4, graduated in 2018, PhD student in UCSC)
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