polar field
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2021 ◽  
Vol 8 (17) ◽  
pp. 2103095
Author(s):  
Kyung Song ◽  
Taewon Min ◽  
Jinsol Seo ◽  
Sangwoo Ryu ◽  
Hyungwoo Lee ◽  
...  

2021 ◽  
Vol 913 (1) ◽  
pp. 65
Author(s):  
Pawan Kumar ◽  
Bidya Binay Karak ◽  
Vindya Vashishth
Keyword(s):  

2021 ◽  
Author(s):  
Soumyaranjan Dash ◽  
Dibyendu Nandy ◽  
Shaonwita Pal
Keyword(s):  

2020 ◽  
Vol 13 (3) ◽  
pp. 71-79
Author(s):  
Irina Ivanovna Shoshina ◽  
Elena Evgenievna Chauzova

Background: The effectiveness of team interaction is often assessed through sociometric indicators, namely sociometric status and emotional reciprocity. At the same time, interpersonal interaction is a cognitive process, since it includes such mental processes as perception, categorization, thinking, speech, etc., which serve for information processing. These individual differences in the way information is processed underlie the concept of cognitive styles. Therefore, cognitive styles can hypothetically be considered as characteristics of interpersonal interaction and a predictor of its effectiveness. Aim: The paper aims to determine the sociometric characteristics of the effectiveness of team interaction of persons with different degree of the field-dependent cognitive style. Materials and methods. To assess field-dependence/field-independence, the Gottschaldt Embedded Figures method was used. The effectiveness of team interaction was assessed using the Moreno small group study method. Statistical analysis was performed with the Mann-Whitney test using IBM SPSS Statistics 23. Results. It was found that persons with a mobile field-dependent cognitive style had a significantly higher hierarchical position and a stable position in the system of nterpersonal relations compared with persons with a polar field-dependent cognitive style. Evidence was obtained on the splitting of field dependence into polar field-dependent and mobile field-dependent styles. Conclusion. Field-dependence/field-independence can be considered as one of the basic inner qualities of a person's intellectual activity, which influences his/her behavior and interpersonal communication.


2020 ◽  
Vol 498 (3) ◽  
pp. 4272-4286
Author(s):  
Simon J Murphy ◽  
Hideyuki Saio ◽  
Masahide Takada-Hidai ◽  
Donald W Kurtz ◽  
Hiromoto Shibahashi ◽  
...  

ABSTRACT Strong magnetic fields in chemically peculiar A-type (Ap) stars typically suppress low-overtone pressure modes (p modes) but allow high-overtone p modes to be driven. KIC 11296437 is the first star to show both. We obtained and analysed a Subaru spectrum, from which we show that KIC 11296437 has abundances similar to other magnetic Ap stars, and we estimate a mean magnetic field modulus of 2.8 ± 0.5 kG. The same spectrum rules out a double-lined spectroscopic binary, and we use other techniques to rule out binarity over a wide parameter space, so the two pulsation types originate in one δ Sct–roAp hybrid pulsator. We construct stellar models depleted in helium and demonstrate that helium settling is second to magnetic damping in suppressing low-overtone p modes in Ap stars. We compute the magnetic damping effect for selected p and g modes, and find that modes with frequencies similar to the fundamental mode are driven for polar field strengths ≲4 kG, while other low-overtone p modes are driven for polar field strengths up to ∼1.5 kG. We find that the high-order g modes commonly observed in γ Dor stars are heavily damped by polar fields stronger than 1–4 kG, with the damping being stronger for higher radial orders. We therefore explain the observation that no magnetic Ap stars have been observed as γ Dor stars. We use our helium-depleted models to calculate the δ Sct instability strip for metallic-lined A (Am) stars, and find that driving from a Rosseland mean opacity bump at ∼5 × 104 K caused by the discontinuous H-ionization edge in bound-free opacity explains the observation of δ Sct pulsations in Am stars.


Author(s):  
Lidia van Driel-Gesztelyi ◽  
Mathew J. Owens

The Sun’s magnetic field drives the solar wind and produces space weather. It also acts as the prototype for an understanding of other stars and their planetary environments. Plasma motions in the solar interior provide the dynamo action that generates the solar magnetic field. At the solar surface, this is evident as an approximately 11-year cycle in the number and position of visible sunspots. This solar cycle is manifest in virtually all observable solar parameters, from the occurrence of the smallest detected magnetic features on the Sun to the size of the bubble in interstellar space that is carved out by the solar wind. Moderate to severe space-weather effects show a strong solar cycle variation. However, it is a matter of debate whether extreme space-weather follows from the 11-year cycle. Each 11-year solar cycle is actually only half of a solar magnetic “Hale” cycle, with the configuration of the Sun’s large-scale magnetic field taking approximately 22 years to repeat. At the start of a new solar cycle, sunspots emerge at mid-latitude regions with an orientation that opposes the dominant large-scale field, leading to an erosion of the polar fields. As the cycle progresses, sunspots emerge at lower latitudes. Around solar maximum, the polar field polarity reverses, but the sunspot orientation remains the same, leading to a build-up of polar field strength that peaks at the start of the next cycle. Similar magnetic cyclicity has recently been inferred at other stars.


2020 ◽  
Author(s):  
Dmitrii Baranov ◽  
Elena Vernova ◽  
Marta Tyasto ◽  
Olga Danilova

<p>On the basis of the synoptic maps of the photospheric magnetic field obtained by the National Solar Observatory Kitt Peak for 1978-2016, a latitude-time diagram of the magnetic field was built. When averaging intensity values over the heliolongitude, the magnetic field sign was taken into account. In order to consider the characteristics of the distribution of weak magnetic fields an upper limit of 5 G was set.</p><p>The latitude-time diagram clearly shows inclined bands corresponding to positive and negative polarity magnetic flows drifting towards the poles of the Sun. Two groups of flows are observed: 1. Relatively narrow bands, with alternating polarity, beginning near the equator and reaching almost the poles of the Sun. Along the time axis, the flow length of one polarity is on the order of 1-2 years; 2. short powerful flows, 3-4.5 years wide, propagating from the spot zone to the poles. These flows reach the poles simultaneously with the begin of the polar field reversal, apparently representing  the so-called “Rush to the Poles” phenomenon.</p><p>The pattern of magnetic field transport is significantly different for the northern and southern hemispheres. Alternating flows of positive and negative polarities most clearly appear in the southern hemisphere during periods of positive polarity of the southern polar field. For the northern hemisphere the picture is much less clear but for individual time intervals alternating flows of opposite polarities can be traced. The slopes of magnetic flux bands allow us to estimate the rate of meridional drift of magnetic fields, which was slightly different for the two hemispheres: V = (16±2) m/s for the southern hemisphere and V = (21±4) m/s for the northern hemisphere. The results obtained indicate that the distribution of weak magnetic fields over the surface of the Sun has a complex structure that is different for the two hemispheres and varies from cycle to cycle.</p>


2019 ◽  
Vol 632 ◽  
pp. A117 ◽  
Author(s):  
Prantika Bhowmik

Aims. Hemispheric irregularities of solar magnetic activity is a well-observed phenomenon, the origin of which has been studied through numerical simulations and data analysis techniques. In this work we explore possible causes generating north-south asymmetry in the reversal timing and amplitude of the polar field during cycle minimum. Additionally, we investigate how hemispheric asymmetry is translated from cycle to cycle. Methods. We pursued a three-step approach. Firstly, we explored the asymmetry present in the observed polar flux and sunspot area by analysing observational data of the last 110 years. Secondly, we investigated the contribution from various factors involved in the Babcock–Leighton mechanism to the evolution and generation of polar flux by performing numerical simulations with a surface flux transport model and synthetic sunspot input profiles. Thirdly, translation of hemispheric asymmetry in the following cycle was estimated by assimilating simulation-generated surface magnetic field maps at cycle minimum in a dynamo simulation. Finally, we assessed our understanding of hemispheric asymmetry in the context of observations by performing additional observational data-driven simulations. Results. Analysis of observational data shows a profound connection between the hemispheric asymmetry in the polar flux at cycle minimum and the total hemispheric activity during the following cycle. We find that the randomness associated with the tilt angle of sunspots is the most crucial element among diverse components of the Babcock–Leighton mechanism in resulting hemispheric irregularities in the evolution of polar field. Our analyses with dynamo simulations indicate that an asymmetric poloidal field at the solar minimum can introduce significant north-south asymmetry in the amplitude and timing of peak activity during the following cycle. While observational data-driven simulations reproduce salient features of the observed asymmetry in the solar cycles during the last 100 years, we speculate that fluctuations in the mean-field α-effect and meridional circulation can have finite contributions in this regard.


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