scholarly journals A large-scale survey of corotating interaction regions and their successors in the outer heliosphere

2000 ◽  
Vol 105 (A1) ◽  
pp. 19-33 ◽  
Author(s):  
P. R. Gazis
Keyword(s):  
Large Scale ◽  
Corotating Interaction Regions ◽  
Outer Heliosphere ◽  
Large Scale Survey ◽  
Interaction Regions

scholarly journals On the origin of variable structures in the winds of hot luminous stars

2013 ◽  
Vol 440 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Yannick J. L. Michaux ◽  
Anthony F. J. Moffat ◽  
André-Nicolas Chené ◽  
Nicole St-Louis
Keyword(s):  
Magnetic Field ◽  
Empirical Evidence ◽  
Temporal Variability ◽  
Large Scale ◽  
Small Scale ◽  
Ionization Zone ◽  
Corotating Interaction Regions ◽  
Wind Variability ◽  
Global Magnetic Field ◽  
Interaction Regions

Abstract Examination of the temporal variability properties of several strong optical recombination lines in a large sample of Galactic Wolf–Rayet (WR) stars reveals possible trends, especially in the more homogeneous WC than the diverse WN subtypes, of increasing wind variability with cooler subtypes. This could imply that a serious contender for the driver of the variations is stochastic, magnetic subsurface convection associated with the 170 kK partial-ionization zone of iron, which should occupy a deeper and larger zone of greater mass in cooler WR subtypes. This empirical evidence suggests that the heretofore proposed ubiquitous driver of wind variability, radiative instabilities, may not be the only mechanism playing a role in the stochastic multiple small-scaled structures seen in the winds of hot luminous stars. In addition to small-scale stochastic behaviour, subsurface convection guided by a global magnetic field with localized emerging loops may also be at the origin of the large-scale corotating interaction regions as seen frequently in O stars and occasionally in the winds of their descendant WR stars.

scholarly journals An extensive spectroscopic time series of three Wolf–Rayet stars – II. A search for wind asymmetries in the dust-forming WC7 binary WR137

2020 ◽  
Vol 497 (4) ◽  
pp. 4448-4458
Author(s):  
N St-Louis ◽  
C Piaulet ◽  
N D Richardson ◽  
T Shenar ◽  
A F J Moffat ◽  
...  
Keyword(s):  
Large Scale ◽  
Rotation Axis ◽  
High Signal ◽  
Double Peak ◽  
Corotating Interaction Regions ◽  
Evolutionary Scenario ◽  
Random Variability ◽  
Interaction Regions ◽  
Peak Emission ◽  
The Continuum

ABSTRACT We present the results of a 4-month, spectroscopic campaign of the Wolf–Rayet dust-making binary, WR137. We detect only small-amplitude random variability in the C iii λ5696 emission line and its integrated quantities (radial velocity, equivalent width, skewness, and kurtosis) that can be explained by stochastic clumps in the wind of the WC star. We find no evidence of large-scale periodic variations often associated with Corotating Interaction Regions that could have explained the observed intrinsic continuum polarization of this star. Our moderately high-resolution and high signal-to-noise average Keck spectrum shows narrow double-peak emission profiles in the H α, H β, H γ, He ii λ6678, and He ii λ5876 lines. These peaks have a stable blue-to-red intensity ratio with a mean of 0.997 and a root mean square of 0.004 commensurate with the noise level; no variability is found during the entire observing period. We suggest that these profiles arise in a decretion disc around the O9 companion, which is thus an O9e star. The characteristics of the profiles are compatible with those of other Be/Oe stars. The presence of this disc can explain the constant component of the continuum polarization of this system, for which the angle is perpendicular to the plane of the orbit, implying that the rotation axis of the O9e star is aligned with that of the orbit. It remains to be explained why the disc is so stable within the strong ultraviolet radiation field of the O star. We present a binary evolutionary scenario that is compatible with the current stellar and system parameters.

Interplanetary Shock-driven Magnetopause Compressions in Gorgon Global-MHD Simulations

2021 ◽  
Author(s):  
Ravindra Desai ◽  
Jonathan Eastwood ◽  
Joseph Eggington ◽  
Mervyn Freeman ◽  
Martin Archer ◽  
...  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Interplanetary Shock ◽  
Interplanetary Shocks ◽  
Pressure Balance ◽  
Interplanetary Coronal Mass Ejections ◽  
Corotating Interaction Regions ◽  
Mhd Simulations ◽  
Interaction Regions ◽  
Space Weather Event

<p>Fast-forward interplanetary interplanetary shocks, as occur at the forefront of interplanetary coronal mass ejections and at corotating interaction regions, can rapidly compress the magnetopause inside the drift paths of electrons and protons, and expose geosynchonous satellites directly to the solar wind.  Here, we use Gorgon Global-MHD simulations to study the response of the magnetopause to different fast-forward interplanetary shocks, with strengths extending from the median shocks observed during solar minimum up to that representing an extreme space weather event. The subsequent magnetopause response can be characterised by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compression well-represented by a power law, and large-scale damped oscillatory motion of the order of an Earth radius, prior to reaching pressure-balance equilibrium. The subsolar magnetopause is found to oscillate with notable frequencies in the range of 2–13 mHz over several periods of diminishing amplitudes.  These results provide an explanation for similar large-scale magnetopause oscillations observed previously during the extreme events of August 1972 and March 1991 and highlight why static magnetopause models break down during periods of strong solar wind driving.</p>

scholarly journals Investigating the origin of cyclical spectral variations in hot, massive stars

2013 ◽  
Vol 9 (S302) ◽  
pp. 334-337
Author(s):  
Alexandre David-Uraz ◽  
Gregg A. Wade ◽  
Véronique Petit ◽  
Asif ud-Doula
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Massive Stars ◽  
Physical Processes ◽  
Corotating Interaction Regions ◽  
Ob Stars ◽  
Wind Variability ◽  
Competing Hypotheses ◽  
Interaction Regions ◽  
Radial Pulsations

AbstractOB stars are known to exhibit various types of wind variability, as detected in their ultraviolet spectra, amongst which are the ubiquitous discrete absorption components (DACs). These features have been associated with large-scale azimuthal structures extending from the base of the wind to its outer regions: corotating interaction regions (CIRs). There are several competing hypotheses as to which physical processes may perturb the star's surface and generate CIRs, including magnetic fields and non radial pulsations (NRPs), the subjects of this paper with a particular emphasis on the former. Although large-scale magnetic fields are ruled out, magnetic spots deserve further investigation, both on the observational and theoretical fronts.

scholarly journals North-south flows observed in the outer heliosphere at solar minimum: Vortex streets or corotating interaction regions?

2001 ◽  
Vol 106 (A8) ◽  
pp. 15973-15984 ◽  
Author(s):  
M. L. Goldstein ◽  
D. A. Roberts ◽  
L. F. Burlaga ◽  
E. Siregar ◽  
A. E. Deane
Keyword(s):  
Solar Minimum ◽  
Corotating Interaction Regions ◽  
Outer Heliosphere ◽  
Vortex Streets ◽  
Interaction Regions

Corotating Interaction Regions in the Outer Heliosphere

1999 ◽  
pp. 269-305 ◽  
Author(s):  
P. R. Gazis ◽  
F. B. McDonald ◽  
R. A. Burger ◽  
S. Chalov ◽  
R. B. Decker ◽  
...  
Keyword(s):  
Corotating Interaction Regions ◽  
Outer Heliosphere ◽  
Interaction Regions

scholarly journals Occurrence and Molecular Variability of Kiwifruit Viruses in Actinidia deliciosa ‘Xuxiang’ in the Shaanxi Province of China

Plant Disease ◽  
2019 ◽  
Vol 103 (6) ◽  
pp. 1309-1318 ◽  
Author(s):  
Lei Zhao ◽  
Wen Yang ◽  
Yuanle Zhang ◽  
Zhanmin Wu ◽  
Qiao-Chun Wang ◽  
...  
Keyword(s):  
Large Scale ◽  
Primary Source ◽  
Potato Virus X ◽  
Shaanxi Province ◽  
Multiple Infection ◽  
First Report ◽  
Molecular Variability ◽  
Large Scale Survey ◽  
Actinidia Spp ◽  
Main Producer

Kiwifruit (Actinidia spp.) is an economically substantial fruit crop with China the main producer. China is the primary source of wild kiwifruit and the largest producer of kiwifruit in terms of both production and planting area, and Shaanxi province is the largest kiwifruit producer in China. Previous studies reported presence of kiwifruit viruses in Actinidia chinensis. In this study, six viruses were identified in kiwifruit ‘Xuxiang’ (A. deliciosa) in Shaanxi, China. The incidence, distribution, and genetic diversity of these viruses were studied. The results showed that Actinidia virus A (AcVA), Actinidia virus B (AcVB), Actinidia chlorotic ringspot-associated virus (AcCRaV), cucumber mosaic virus (CMV), apple stem grooving virus (ASGV), and potato virus X (PVX) were the main viruses infecting Xuxiang kiwifruit in Shaanxi, China. Incidence of the various viruses with both single and multiple infection varied with different kiwifruit-growing counties. For single virus infection, the highest and the lowest numbers of samples infected were about 22 for AcCRaV and 0 for AcVB in Meixian out of 170 samples, 12 for AcVA and 0 for CMV in Zhouzhi out of 120 samples, 10 for AcVA and 0 for AcVB, AcCRaV, ASGV, PVX, and CMV in Yangling out of 70 samples, and 8 for AcCRaV and CMV and 0 for AcVA, AcVB, ASGV, and PVX in Hanzhong out of 80 samples, respectively. Samples which were multiply infected with two or more viruses were also detected. Analysis of the phylogenetic tree of these viruses showed some genetic variability in the AcVA, AcVB, and AcCRaV isolates of Shaanxi kiwifruit. There was no obvious molecular variation in the coat protein genes of ASGV, CMV, and PVX virus isolates from Shaanxi kiwifruit. The present study is the first large-scale survey of kiwifruit viruses in Shaanxi, China. To our knowledge, this is the first report of PVX infecting kiwifruit and the first report of molecular variability of AcVA, AcVB, and AcCRaV. These results provide important data for studying the genetic evolution of AcVA, AcVB, AcCRaV, ASGV, CMV, and PVX.

scholarly journals Correcting Citizens’ Misperceptions about non-Western Immigrants: Corrective Information, Interpretations, and Policy Opinions

2020 ◽  
pp. 1-10 ◽  
Author(s):  
Frederik Juhl Jørgensen ◽  
Mathias Osmundsen
Keyword(s):  
Immigration Policy ◽  
Large Scale ◽  
Total Population ◽  
Survey Experiment ◽  
Correct Information ◽  
The Usa ◽  
Large Scale Survey ◽  
Nationally Representative ◽  
Information Change ◽  
Corrective Information

Abstract Can corrective information change citizens’ misperceptions about immigrants and subsequently lead to favorable immigration opinions? While prior studies from the USA document how corrections about the size of minority populations fail to change citizens’ immigration-related opinions, they do not examine how other facts that speak to immigrants’ cultural or economic dependency rates can influence immigration policy opinions. To extend earlier work, we conducted a large-scale survey experiment fielded to a nationally representative sample of Danes. We randomly expose participants to information about non-Western immigrants’ (1) welfare dependency rate, (2) crime rate, and (3) proportion of the total population. We find that participants update their factual beliefs in light of correct information, but reinterpret the information in a highly selective fashion, ultimately failing to change their policy preferences.

Sign in / Sign up

Export Citation Format

Share Document