scholarly journals Helicity and The Alpha-Effect: Dynamo Theory and Observations

2005 ◽  
Vol 13 ◽  
pp. 95-96
Author(s):  
Kirill Kuzanyan
Keyword(s):  
Active Regions ◽  
Dynamo Theory ◽  
Solar Convection Zone ◽  
Representative Sampling ◽  
Solar Convection ◽  
Spatial And Temporal Distributions ◽  
Twist Factor ◽  
Chinese Academy Of Sciences ◽  
Alpha Effect ◽  
Academy Of Sciences

AbstractSpatial and temporal distributions of tracers of the alpha-effect in the solar convection zone, such as current helicity and twist factor averaged over solar active regions are available by vector magnetographic observations. We discuss the data obtained at Huairou Solar Observing Station of Chinese Academy of Sciences and confront them with predictions of dynamo theory. At the present time, though the observations are rough, we still have a statistically representative sampling to conclude that the observations do not contradict the theory.

scholarly journals Magnetic Helicity Propagation from Inside the Sun

2005 ◽  
Vol 13 ◽  
pp. 97-100
Author(s):  
Dana Longcope
Keyword(s):  
Active Region ◽  
Flux Tube ◽  
Convection Zone ◽  
Active Regions ◽  
Magnetic Helicity ◽  
The Sun ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Region Emergence

AbstractModels of twisted flux tube evolution provide a picture of how magnetic helicity is propagated through the solar convection zone into the corona. According to the models, helicity tends toward an approximately uniform length-density along a tube, rather than concentrating at wider portions. Coronal fields lengthen rapidly during active region emergence, requiring additional helicity to propagate from the submerged flux tube. Recent observations of emerging active regions show an evolution consistent with this prediction, and no evidence of helicity concentrating in wider sections.

scholarly journals Magnetic fields in the solar convection zone

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Yuhong Fan
Keyword(s):  
Magnetic Field ◽  
Convection Zone ◽  
Active Regions ◽  
Toroidal Magnetic Field ◽  
Near Surface ◽  
New Developments ◽  
Solar Convection Zone ◽  
Flux Tubes ◽  
Solar Convection ◽  
Dynamo Mechanism

AbstractIt has been a prevailing picture that active regions on the solar surface originate from a strong toroidal magnetic field stored in the overshoot region at the base of the solar convection zone, generated by a deep seated solar dynamo mechanism. This article reviews the studies in regard to how the toroidal magnetic field can destabilize and rise through the convection zone to form the observed solar active regions at the surface. Furthermore, new results from the global simulations of the convective dynamos, and from the near-surface layer simulations of active region formation, together with helioseismic investigations of the pre-emergence active regions, are calling into question the picture of active regions as buoyantly rising flux tubes originating from the bottom of the convection zone. This article also gives a review on these new developments.

scholarly journals Formation of Arching Flux Tubes at the Base of the Solar Convection Zone

2001 ◽  
Vol 203 ◽  
pp. 273-275
Author(s):  
Y. Fan
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Linear Growth ◽  
Convection Zone ◽  
Active Regions ◽  
Solar Convection Zone ◽  
Flux Tubes ◽  
Solar Convection ◽  
Neutrally Buoyant ◽  
Dynamo Process

Solar active regions are believed to correspond to the topmost portions of Ω-shaped arching flux tubes that have risen buoyantly from the base of the solar convection zone, where strong toroidal magnetic fields are being generated by the dynamo process. The development of such emerging Ω-loops is likely a result of the buoyant instability associated with the submerged toroidal magnetic field. Using an anelastic MHD code, we simulate the formation of buoyant, arching flux tube structures as a result of the non-linear growth of the undular instability of a neutrally buoyant layer of horizontal, unidirectional magnetic field at the base of the solar convection zone.

scholarly journals Vorticity, Current Helicity and Alpha-effect for Magnetic-driven Turbulence in the Solar Convection Zone

2001 ◽  
Vol 203 ◽  
pp. 152-155
Author(s):  
G. Rüdiger
Keyword(s):  
Numerical Simulation ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Electromotive Force ◽  
Convection Zone ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

The turbulent electromotive force as well as the kinetic and current helicities have been computed for a turbulence subject to magnetic buoyancy and global rotation. The dynamo-alpha is found as positive in the northern hemisphere and negative in the southern hemisphere and the kinetic helicity has just the same signs.In agreement with the observations the current helicity is negative in the northern hemisphere and positive in the southern hemisphere. Our current helicities and alpha-effects are thus always out of phase. The signs of alpha-effect and both helicities exactly correspond to a numerical simulation by Brandenburg & Schmitt (1998).

scholarly journals Preface to the Interfacial Science Developments at the Chinese Academy of Sciences Virtual Special Issue

Langmuir ◽  
2020 ◽  
Vol 36 (41) ◽  
pp. 12087-12087 ◽  
Author(s):  
Yilin Wang ◽  
Shaoyi Jiang ◽  
Zhan Chen ◽  
Shu-Hong Yu ◽  
Gilbert Walker
Keyword(s):  
Special Issue ◽  
Interfacial Science ◽  
Chinese Academy Of Sciences ◽  
Academy Of Sciences

Two new species of the spider genus Pholcus Walckenaer, 1805 (Araneae: Pholcidae) from Pakistan

Zootaxa ◽  
2020 ◽  
Vol 4820 (1) ◽  
pp. 177-185
Author(s):  
TIANQI LAN ◽  
ZHIYUAN YAO ◽  
ABID ALI ◽  
GUO ZHENG ◽  
SHUQIANG LI
Keyword(s):  
New Species ◽  
Species Group ◽  
Male And Female ◽  
Female Type ◽  
Chinese Academy Of Sciences ◽  
Two New Species ◽  
Academy Of Sciences ◽  
Gilgit Baltistan ◽  
First Time ◽  
Beijing China

The genus Pholcus Walckenaer, 1805 is reported from Pakistan for the first time. Two new species of the Pholcus nenjukovi species-group are described: Pholcus hamuchal Yao & Li sp. nov. (Gilgit Baltistan, male and female) and Pholcus kalam Yao & Li sp. nov. (Khyber Pakhtunkhwa, male and female). Type material is deposited in the Institute of Zoology, Chinese Academy of Sciences (IZCAS) in Beijing, China.

Sign in / Sign up

Export Citation Format

Share Document