Yutian Chi, Chenglong Shen, Long Cheng, Bingkun Yu, Bin Miao, Yuming Wang, Tielong Zhang, Zhuxuan Zou, Mengjiao Xu, Zonghao Pan, Zhenpeng Su, Jingnan Guo, Dongwei Mao, Zhihui Zhong, Zhiyong Zhang, Junyan Liu, Can Wang, Zhiyong Wu, Guoqiang Wang, Sudong Xiao, Kai Liu, Xinjun Hao, Yiren Li, Manming Chen, Yang Du
Tianwen-1 spacecraft (Wan et al. 2020) is China's first Mars exploration mission. The Mars Orbiter Magnetometer (MOMAG) is a scientific instrument aboard the Tianwen-1 mission that is designed to study magnetic fields at Mars, including the solar wind to the magnetosheath and the ionosphere. Using the first Tianwen-1/MOMAG data that is publicly available, we present interplanetary coronal mass ejection (ICME) and stream interaction region (SIR) catalogues based on in-situ observations at Mars between November 16, 2021, and December 31, 2021. We compared the magnetic field intensity and vector magnetic field measurements from Tianwen-1/MOMAG and Mars Atmospheric Volatile EvolutioN (MAVEN)/MAG during the ICME and SIR interval and found a generally good consistency between them. Due to MAVEN's orbital adjustment since 2019, the Tianwen-1/MOMAG instrument is currently the almost unique interplanetary magnetic field monitor at Mars. The observations indicate that the MOMAG instrument on Tianwen-1 is performing well and can provide accurate measurements of the vector magnetic field in the near-Mars solar wind space. The multi-point observations combining MOMAG, MINPA, and MEPA on board Tianwen-1 with MAG, SWIA, and STATIC on board MAVEN will open a window to systematically study the characteristic of ICMEs and SIRs at Mars, and their influences on the Martian atmosphere and ionosphere.
Jiajia Liu, Yuming Wang, Chenglong Shen, Kai Liu, Zonghao Pan, S. Wang
Nov 19, 2015·astro-ph.SR·PDF We present the multi-point and multi-wavelength observation and analysis on a solar coronal jet and coronal mass ejection (CME) event in this paper. Employing the GCS model, we obtained the real (three-dimensional) heliocentric distance and direction of the CME and found it propagate in a high speed over 1000 km/s . The jet erupted before and shared the same source region with the CME. The temporal and spacial relation- ship between them guide us the possibility that the jet triggered the CME and became its core. This scenario could promisingly enrich our understanding on the triggering mechanism of coronal mass ejections and their relations with coronal large-scale jets. On the other hand, the magnetic field configuration of the source region observed by the SDO/HMI instrument and the off- limb inverse Y-shaped configuration observed by SDO/AIA 171 A passband, together provide the first detailed observation on the three-dimensional reconnection process of large-scale jets as simulated in Pariat et al. 2009. The erupting process of the jet highlights that filament-like materials are important during the eruption not only of small-scale X-ray jets (Sterling et al. 2015) but also probably of large-scale EUV jets. Based on our observation and analysis, we propose a most possible mechanism for the whole event with a blob structure overlaying the three-dimensional structure of the jet to describe the interaction between the jet and the CME.
Chenglong Shen, Yuming Wang, Zonghao Pan, Min Zhang, Pinzhong Ye, S. Wang
Mar 17, 2013·astro-ph.SR·PDF The projection effect is one of the biggest obstacles in learning the real properties of coronal mass ejections (CMEs) and forecasting their geoeffectiveness. To evaluate the projection effect, 86 full halo CMEs (FHCMEs) listed in the CDAW CME catalog from 2007 March 1 to 2012 May 31 are investigated. By applying the Graduated Cylindrical Shell (GCS) model, we obtain the de-projected values of the propagation velocity, direction and angular width of these FHCMEs, and compare them with the projected values measured in the plane-of-sky. Although these CMEs look full halo in the view angle of SOHO, it is found that their propagation directions and angular widths could vary in a large range, implying projection effect is a major reason causing a CME being halo, but not the only one. Furthermore, the comparison of the de-projected and projected velocities reveals that most FHCMEs originating within 45$^\circ$ of the Sun-Earth line with a projected speed slower than 900 km s$^{-1}$ suffer from large projection effect, while the FHCMEs originating far from the vicinity of solar disk center or moving faster than 900 km s$^{-1}$ have small projection effect. The results suggest that not all of FHCMEs need to correct projection effect for their velocities.
Zhuxuan Zou, Yuming Wang, Tielong Zhang, Guoqiang Wang, Sudong Xiao, Zonghao Pan, Zhoubin Zhang, Wei Yan, Yang Du, Yutian Chi, Long Cheng, Zhiyong Wu, Xinjun Hao, Yiren Li, Kai Liu, Manming Chen, Zhenpeng Su, Chenglong Shen, Mengjiao Xu, Jingnan Guo
Mars Orbiter Magnetometer (MOMAG) is one of seven science payloads onboard Tianwen-1's orbiter. Unlike most of the satellites, Tianwen-1's orbiter is not magnetically cleaned, and the boom where placed the magnetometer's sensors is not long enough. These pose many challenges to the magnetic field data processing. In this paper, we introduce the in-flight calibration process of the Tianwen-1/MOMAG. The magnetic interference from the spacecraft, including spacecraft generated dynamic field and slowly-changing offsets are cleaned in sequence. Then the calibrated magnetic field data are compared with the data from the Mars Atmosphere and Volatile EvolutioN (MAVEN). We find that some physical structures in the solar wind are consistent between the two data sets, and the distributions of the magnetic field strength in the solar wind are very similar. These results suggest that the in-flight calibration of the MOMAG is successful and the MOMAG provides reliable data for scientific research.
Yuming Wang, Tielong Zhang, Guoqiang Wang, Sudong Xiao, Zhuxuan Zou, Long Cheng, Zonghao Pan, Kai Liu, Xinjun Hao, Yiren Li, Manming Chen, Zhoubin Zhang, Wei Yan, Zhenpeng Su, Zhiyong Wu, Chenglong Shen, Yutian Chi, Mengjiao Xu, Jingnan Guo, Yang Du
Mars Orbiter MAGnetometer (MOMAG) is a scientifc instrument onboard the orbiter of China's first mission for Mars -- Tianwen-1. It started to routinely measure the magnetic field from the solar wind to magnetic pile-up region surrounding Mars since November 13, 2021. Here we present its in-flight performance and first science results based on the first one and a half months' data. By comparing with the magnetic field data in the solar wind from the Mars Atmosphere and Volatile EvolutioN (MAVEN), the magnetic field by MOMAG is at the same level in magnitude, and the same magnetic structures with the similar variations in three components could be found in MOMAG data. In the first one and a half months, we recognize 158 clear bow shock (BS) crossings from MOMAG data, whose locations statistically match well with the modeled average BS. We also identify 5 pairs of simultaneous BS crossings of the Tianwen-1's orbiter and MAVEN. These BS crossings confirm the global shape of modeled BS as well as the south-north asymmetry of the Martian BS. Two presented cases in this paper suggest that the BS is probably more dynamic at flank than near the nose. So far, MOMAG performs well, and provides accurate magnetic field vectors. MOMAG is continuously scanning the magnetic field surrounding Mars. These measurements complemented by observations from MAVEN will undoubtedly advance our understanding of the plasma environment of Mars.
Chenglong Shen, Yuming Wang, Zonghao Pan, Bin Miao, Pinzhong Ye, S. Wang
Jun 18, 2014·astro-ph.SR·PDF A geomagnetic storm is mainly caused by a front-side coronal mass ejection (CME) hitting the Earth and then interacting with the magnetosphere. However, not all front-side CMEs can hit the Earth. Thus, which CMEs hit the Earth and when they do so are important issues in the study and forecasting of space weather. In our previous work (Shen et al., 2013), the de-projected parameters of the full-halo coronal mass ejections (FHCMEs) that occurred from 2007 March 1 to 2012 May 31 were estimated, and there are 39 front-side events could be fitted by the GCS model. In this work, we continue to study whether and when these front-side FHCMEs (FFHCMEs) hit the Earth. It is found that 59\% of these FFHCMEs hit the Earth, and for central events, whose deviation angles $ε$, which are the angles between the propagation direction and the Sun-Earth line, are smaller than 45 degrees, the fraction increases to 75\%. After checking the deprojected angular widths of the CMEs, we found that all of the Earth-encountered CMEs satisfy a simple criterion that the angular width ($ω$) is larger than twice the deviation angle ($ε$). This result suggests that some simple criteria can be used to forecast whether a CME could hit the Earth. Furthermore, for Earth-encountered CMEs, the transit time is found to be roughly anti-correlated with the de-projected velocity, but some events significantly deviate from the linearity. For CMEs with similar velocities, the differences of their transit times can be up to several days. Such deviation is further demonstrated to be mainly caused by the CME geometry and propagation direction, which are essential in the forecasting of CME arrival.
Jiajia Liu, Yuming Wang, Robertus Erdelyi, Rui Liu, Scott W. McIntosh, Tingyu Gou, Jun Chen, Kai Liu, Lijuan Liu, Zonghao Pan
Aug 27, 2016·astro-ph.SR·PDF In this paper, we present the detailed analysis of recurrent homologous jets originating from an emerging negative magnetic flux at the edge of an Active Region. The observed jets show multi-thermal features. Their evolution shows high consistence with the characteristic parameters of the emerging flux, suggesting that with more free magnetic energy, the eruptions tend to be more violent, frequent and blowout-like. The average temperature, average electron number density and axial speed are found to be similar for different jets, indicating that they should have been formed by plasmas from similar origins. Statistical analysis of the jets and their footpoint region conditions reveals a strong positive relationship between the footpoint-region total 131 Å intensity enhancement and jets' length/width. Stronger linearly positive relationships also exist between the total intensity enhancement/thermal energy of the footpoint regions and jets' mass/kinetic/thermal energy, with higher cross-correlation coefficients. All the above results, together, confirm the direct relationship between the magnetic reconnection and the jets, and validate the important role of magnetic reconnection in transporting large amount of free magnetic energy into jets. It is also suggested that there should be more free energy released during the magnetic reconnection of blowout than of standard jet events.