scholarly journals IUE Observations of the Chromospheric Activity-Age Relation in Young Solar-Type Stars

1983 ◽  
Vol 102 ◽  
pp. 161-164
Author(s):  
Theodore Simon ◽  
Ann Merchant Boesgaard
Keyword(s):  
Magnetic Fields ◽  
Flare Activity ◽  
The Sun ◽  
Late Type ◽  
Cool Star ◽  
Opportune Time ◽  
Solar Type ◽  
Age Relation ◽  
Relationship Of ◽  
The Relationship

The difficulties of measuring magnetic fields in late-type stars other than the sun are well known, as one is reminded by other contributions to these Proceedings. This Symposium nevertheless comes at a very opportune time, as we are now at the point where we can begin to explore the relationship of stellar magnetism to flare activity and quiescent cool star chromospheres, transition regions (TRs), and coronae.

A Search for Dyson Spheres around Late-Type Stars in the Solar Neighborhood II

1997 ◽  
Vol 161 ◽  
pp. 707-709 ◽  
Author(s):  
Jun Jugaku ◽  
Shiro Nishimura
Keyword(s):  
Solar Neighborhood ◽  
The Sun ◽  
Late Type ◽  
Solar Type

AbstractWe continued our search for partial (incomplete) Dyson spheres associated with 50 solar-type stars (spectral classes F, G, and K) within 25 pc of the Sun. No candidate objects were found.

scholarly journals The frequency of stellar X-ray flares from a large-scale XMM-Newton sample

2015 ◽  
Vol 11 (S320) ◽  
pp. 134-137
Author(s):  
John P. Pye ◽  
Simon R. Rosen
Keyword(s):  
Solar System ◽  
Solar Flare ◽  
Space Weather ◽  
White Light ◽  
Large Scale ◽  
The Sun ◽  
X Ray ◽  
Cool Star ◽  
Exoplanetary Systems ◽  
Solar Type

AbstractWe present estimates of cool-star X-ray flare rates determined from the XMM-Tycho survey (Pyeet al. 2015, A&A, 581, A28), and compare them with previously published values for the Sun and for other stellar EUV and white-light samples. We demonstrate the importance of applying appropriate corrections, especially in regard to the total, effective size of the stellar sample. Our results are broadly consistent with rates reported in the literature for Kepler white-light flares from solar-type stars, and with extrapolations of solar flare rates, indicating the potential of stellar X-ray flare observations to address issues such as ‘space weather’ in exoplanetary systems and our own solar system.

scholarly journals Hubungan Modal Sosial dengan Partisipasi Kelompok Tani dalam Koperasi Pondok Pesantren (Kopontren)

2018 ◽  
Vol 2 (3) ◽  
pp. 347
Author(s):  
Irfan Fadhlurrahman ◽  
Saharuddin Saharuddin
Keyword(s):  
Social Capital ◽  
Educational Institution ◽  
Strong Relationship ◽  
Individual Characteristics ◽  
Individual Characteristic ◽  
Group Members ◽  
Age Relation ◽  
Farmer Groups ◽  
Relationship Of ◽  
The Relationship

ABSTRACTCooperatives as one of the sectors of economic power that is considered the most suitable developed in Indonesia, because formed by members and aims for the welfare of its members. Pesantren as a grassroots Islamic educational institution also develops Koperasi Pondok Pesantren (Kopontren) by fostering farmer groups. The purpose of this study is to analyze the relationship of individual characteristics (age, education level, length of work, and income level), social capital, and participation of farmer group members in Kopontren Alif agribusiness activities. The result of the research shows that there is no significant correlation between individual characteristic with social capital and participation, except the age relation with participation, but the relation is negative. While social capital with participation has a significant and strong relationship. This is due to the high social capital with the participation of farmer group members in the activities of Kopontren Alif agribusiness.Keywords: farmer groups, individual characteristic, kopontren, social capital, participation. ABSTRAKKoperasi sebagai salah satu sektor kekuatan ekonomi yang dianggap paling cocok dikembangkan di Indonesia, karena dibentuk oleh anggota dan bertujuan untuk kesejahteraan anggotanya. Pesantren sebagai lembaga pendidikan Islam yang bersifat akar rumput turut mengembangkan koperasi pondok pesantren (Kopontren) dengan membina kelompok tani. Tujuan penelitian ini adalah menganalisis hubungan karakteristik individu (usia, tingkat pendidikan, lama bekerja, dan tingkat pendapatan), modal sosial, dan partisipasi anggota kelompok tani binaan dalam kegiatan agribisnis Kopontren Alif. Hasil penelitian yang diperoleh menunjukkan bahwa tidak terdapat hubungan signifikan antara karakteristik individu dengan modal sosial dan partisipasi, kecuali hubungan usia dengan partisipasi, namun hubungannya negatif. Sedangkan modal sosial dengan partisipasi memiliki hubungan yang signifikan dan kuat. Hal ini dikarenakan tingginya modal sosial dengan partisipasi anggota kelompok tani dalam kegiatan agribisnis Kopontren Alif.Kata kunci: karakteristik individu, kelompok tani, kopontren, modal sosial, partisipasi.

scholarly journals The magnetic field of the nearest cool star A Paradigm for Stellar Activity

1996 ◽  
Vol 176 ◽  
pp. 1-16
Author(s):  
Carolus J. Schrijver
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Differential Rotation ◽  
Stellar Atmospheres ◽  
The Sun ◽  
Flux Tubes ◽  
Cool Star ◽  
Temperature Regimes ◽  
The Magnetic Field ◽  
Selection Of

Looking at the Sun forges the framework within which we try to interpret stellar observations. The stellar counterparts of spots, plages, flux tubes, chromospheres, coronae, etc., are readily invoked when attempting to interpret stellar data. This review discusses a selection of solar phenomena that are crucial to understand stellar atmospheric activity. Topics include the interaction of magnetic fields and flows, the relationships between fluxes from different temperature regimes in stellar atmospheres, the photospheric flux budget and its impact on the measurement of the dynamo strength, and the measurement of stellar differential rotation.

scholarly journals Flare Activity in Algol-type Binaries

1995 ◽  
Vol 151 ◽  
pp. 193-194
Author(s):  
Izold Pustylnik
Keyword(s):  
Convection Zone ◽  
Scale Height ◽  
The Other ◽  
Flare Activity ◽  
Low Density ◽  
Late Type ◽  
X Ray ◽  
Relative Contribution ◽  
Shock Region ◽  
Solar Type

Two sites of flare activity have been identified in Algol-type binaiies. One is associated with the shock region from the accretion on B-A type primary, another, predominant one is apparently connected with coronal mass ejections (CME) from the late-type, Roche lobe filling secondary. The relative contribution from both sources of activity is still to be found. According to Peters & Polidan (1984), a moderately hot (105 K) and low density ne ≃ 109 cm−3 high turbulent accretion region (HTAR) surrounding the hot component has been discovered. Typical dimensions of HTAR agree with the scale height of the X-ray source HX ≃ 1.2 · 1011 · T7 cm (Harnden et al 1977), where T7 is the temperature in units of 107 K. But the decay time of the HTAR, comparable to the orbital period, more favourably agrees with the idea of CME as deduced from Ginga observations of X-ray flares on Algol (Stern et al. 1992). One solution of the controversy as to the contribution from HTAR would be to concentrate on X-ray observations of systems like u Her and U CrB, where the secondary is possibly earlier than FO (thus, is not expected to possess an extensive convection zone) and on the other hand on systems like U Cep, where during periods of high activity Ṁ ≃ 10−6M⊙ per year. Thus, the accretion luminosity must be at least by two orders of magnitude higher than in Algol. At present the analysis of X-ray flares is based upon the solar type CME assuming different scenarios of radiative and/or conductive cooling (see Stern et al. 1992). However, the current models of CME do not take into account the binary nature of the flaring object.

scholarly journals Study of the effects of magnetic braking on the lithium abundances of the Sun and solar-type stars

2020 ◽  
Vol 496 (2) ◽  
pp. 1343-1354
Author(s):  
R Caballero Navarro ◽  
A García Hernández ◽  
A Ayala ◽  
J C Suárez
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Globular Clusters ◽  
Main Sequence ◽  
The Sun ◽  
Depletion Rate ◽  
Solar Type ◽  
Magnetic Braking ◽  
Physical Phenomena ◽  
The Impact

ABSTRACT The study of lithium (Li) surface abundance in the Sun and young stellar globular clusters which are seemingly anomalous in present-day scenarios, as well as the influence of rotation and magnetic braking (MB) on its depletion during pre-main sequence (PMS) and main sequence (MS). In this work, the effects of rotational mixing and of the rotational hydrostatic effects on Li abundances are studied by simulating several grids of PMS and MS rotating and non-rotating models. Those effects are combined with the additional impact of the MB (with magnetic field intensities ranging between 3.0 and 5.0 G). The data obtained from simulations are confronted by comparing different stellar parameters. The results show that the surface Li abundance for the Sun-like models at the end of the PMS and throughout the MS decreases when rotational effects are included, that is the Li depletion rate for rotating models is higher than for non-rotating ones. This effect is attenuated when the MB produced by a magnetic field is present. This physical phenomena impacts also the star effective temperature (Teff) and its location in the HR diagram. The impact of MB in Li depletion is sensitive to the magnetic field intensity: the higher it is, the lower the Li destruction. A direct link between the magnetic fields and the convective zone (CZ) size is observed: stronger magnetic fields produce shallower CZ’s. This result suggests that MB effect must be taken into consideration during PMS if we aim to reproduce Li abundances in young clusters.

scholarly journals GOOD AND OTHER IDEAS OF PLATO

2018 ◽  
Keyword(s):  
Clear Understanding ◽  
The Sun ◽  
Special Place ◽  
Theory Of Ideas ◽  
Definition Of ◽  
Relationship Of ◽  
Religious Nature ◽  
Theory Of Forms ◽  
The Relationship ◽  
Ethics And Politics

The article analyzes Plato’s doctrine of forms, discusses whether the use of the concept of Plato’s theory of ideas (forms) is justified, noted that Plato’s views on this matter are inconsistent and contradictory and that there is, in fact, no theory of forms in Plato’s philosophy. A special place in the philosophy of Plato is the idea of good, which he treats as the highest idea. An analysis of the Platonic understanding of good shows that there is no clear and articulated explanation for Plato in relation to this idea. Plato has the idea of good, but he has no conception of good, and he speaks about good without the expanded definition of this concept. To explain the content of the idea of good, Plato uses allegories. The most famous of them is the likeness of the good of the Sun in the «Politeia» dialogue. The article poses the question of why Plato needed the concept of «idea» and «good» if he did not have a clear understanding of what they are. The author believes that there are two reasons for this. The first of them is pedagogical: Plato deliberately does not answer any of the important issues related to the existence of ideas, the relationship of ideas and things, the relationship between the ideas themselves. Plato reveals all these difficulties, but gives his readers the opportunity to understand these problems independently. The second reason is that Plato’s ideas are not intended for the knowledge of being, they are not philosophical categories. This is especially evident in the case of a good idea. The author of the article concludes that the notion of good first appears in Platos ethics and only then becomes ontological. Plato’s ontology in general is intended to justify his ethics and politics. Proceeding from this, the author comes to the conclusion that the ideas of Plato have a religious nature, and Plato himself is not a philosopher, but a myth-creator, a religious prophet and a teacher.

A proposal for an electrical connection between the gravitational field and light

2020 ◽  
Vol 33 (3) ◽  
pp. 271-275
Author(s):  
Michael J. Curran
Keyword(s):  
Gravitational Field ◽  
Magnetic Fields ◽  
Gravitational Waves ◽  
Building Block ◽  
Electromagnetic Waves ◽  
Direct Photon ◽  
The Sun ◽  
Speed Of Light ◽  
Electrical Connection ◽  
The Relationship

Based on well-established equations, we provide evidence of an electrical connection between the gravitational field and light. Each is modeled using the inductance‐capacitance ( <mml:math display="inline"> <mml:mrow> <mml:mi>L</mml:mi> <mml:mi>C</mml:mi> </mml:mrow> </mml:math> ) circuit as the building block. A proposed direct photon force (not a pressure and not by means of a force carrier), the relationship between the speed of light and gravity, the frequency and wavelength of gravitational waves, gravitational redshift, the trajectory of planets around the sun, and equations of plane electromagnetic waves may all be expressed with the assistance of an ideal (no resistance) <mml:math display="inline"> <mml:mrow> <mml:mi>L</mml:mi> <mml:mi>C</mml:mi> </mml:mrow> </mml:math> circuit model of light. Each begins with the Planck‐Einstein relationship. Each suggests that gravity and electromagnetism interact directly through fluctuating electrical and magnetic fields from both sources. With this perspective Einstein's concept of the warping of spacetime may not be needed to explain gravitation.

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