TY  - JOUR
A1  - Cheng, X.
A1  - Ding, M. D.
A1  - Zhang, J.
A1  - Sun, X. D.
A1  - Guo, Y.
A1  - Wang, Yi-Ming
A1  - Kliem, Bernhard
A1  - Deng, Y. Y.
T1  - Formation of a double-decker magnetic flux rope in the sigmoidal solar active region 11520
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s(-1). The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.
KW  - Sun: corona
KW  - Sun: coronal mass ejections (CMEs)
KW  - Sun: filaments, prominences
KW  - Sun: magnetic fields
Y1  - 2014
U6  - https://doi.org/10.1088/0004-637X/789/2/93
SN  - 0004-637X
SN  - 1538-4357
VL  - 789
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Meijer, Niels
A1  - Dupont-Nivet, Guillaume
A1  - Abels, Hemmo A.
A1  - Kaya, Mustafa Y.
A1  - Licht, Alexis
A1  - Xiao, Meimei
A1  - Zhang, Yang
A1  - Roperch, Pierrick
A1  - Poujol, Marc
A1  - Lai, Zhongping
A1  - Guo, Zhaojie
T1  - Central Asian moisture modulated by proto-Paratethys Sea incursions since the early Eocene
JF  - Earth and planetary science letters
N2  - The establishment and evolution of the Asian monsoons and arid interior have been linked to uplift of the Tibetan Plateau, retreat of the inland proto-Paratethys Sea and global cooling during the Cenozoic. However, the respective role of these driving mechanisms remains poorly constrained. This is partly due to a lack of continental records covering the key Eocene epoch marked by the onset of Tibetan Plateau uplift, proto-Paratethys Sea incursions and long-term global cooling. In this study, we reconstruct paleoenvironments in the Xining Basin, NE Tibet, to show a long-term drying of the Asian continental interior from the early Eocene to the Oligocene. Superimposed on this trend are three alternations between arid mudflat and wetter saline lake intervals, which are interpreted to reflect atmospheric moisture fluctuations in the basin. We date these fluctuations using magnetostratigraphy and the radiometric age of an intercalated tuff layer. The first saline lake interval is tentatively constrained to the late Paleocene-early Eocene. The other two are firmly dated between similar to 46 Ma (top magnetochron C21n) and similar to 41 Ma (base C18r) and between similar to 40 Ma (base C18n) and similar to 37 Ma (top C17n). Remarkably, these phases correlate in time with highstands of the proto-Paratethys Sea. This strongly suggests that these sea incursions enhanced westerly moisture supply as far inland as the Xining Basin. We conclude that the proto-Paratethys Sea constituted a key driver of Asian climate and should be considered in model and proxy interpretations. (C) 2019 Elsevier B.V. All rights reserved.
KW  - Paleogene
KW  - magnetostratigraphy
KW  - Central Asia
KW  - Xining Basin
KW  - westerlies
KW  - Asian monsoon
Y1  - 2019
U6  - https://doi.org/10.1016/j.epsl.2018.12.031
SN  - 0012-821X
SN  - 1385-013X
VL  - 510
SP  - 73
EP  - 84
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Licht, A.
A1  - van Cappelle, M.
A1  - Abels, Hemmo A.
A1  - Ladant, J. -B.
A1  - Trabucho-Alexandre, J.
A1  - France-Lanord, C.
A1  - Donnadieu, Y.
A1  - Vandenberghe, J.
A1  - Rigaudier, T.
A1  - Lecuyer, C.
A1  - Terry, D.
A1  - Adriaens, R.
A1  - Boura, A.
A1  - Guo, Z.
A1  - Soe, Aung Naing
A1  - Quade, J.
A1  - Dupont-Nivet, Guillaume
A1  - Jaeger, J. -J.
T1  - Asian monsoons in a late Eocene greenhouse world
JF  - Nature : the international weekly journal of science
N2  - The strong present-day Asian monsoons are thought to have originated between 25 and 22 million years (Myr) ago, driven by Tibetan-Himalayan uplift. However, the existence of older Asian monsoons and their response to enhanced greenhouse conditions such as those in the Eocene period (55-34Myrago) are unknown because of the paucity of well-dated records. Here we show late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan-Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China. Our climate simulations support modern-like Eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhanced greenhouse conditions counterbalanced the negative effect of lower Tibetan relief on precipitation. These strong monsoons later weakened with the global shift to icehouse conditions 34 Myr ago.
Y1  - 2014
U6  - https://doi.org/10.1038/nature13704
SN  - 0028-0836
SN  - 1476-4687
VL  - 513
IS  - 7519
SP  - 501
EP  - +
PB  - Nature Publ. Group
CY  - London
ER  -