scholarly journals Rotation Period of the Sun 1

Nature ◽  
1911 ◽  
Vol 88 (2195) ◽  
pp. 112-113
Author(s):  
CHARLES P. BUTLER
Keyword(s):  
Rotation Period ◽  
The Sun

Formation of current sheets and plasmoids within corotating/stream interaction regions

2020 ◽  
Author(s):  
Timofey Sagitov ◽  
Roman Kislov
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Hole ◽  
High Speed ◽  
Solar Rotation ◽  
Coronal Holes ◽  
Rotation Period ◽  
The Sun ◽  
Current Sheets ◽  
Interaction Regions

<p>High speed streams originating from coronal holes are long-lived plasma structures that form corotating interaction regions (CIRs) or stream interface regions (SIRs) in the solar wind. The term CIR is used for streams existing for at least one solar rotation period, and the SIR stands for streams with a shorter lifetime. Since the plasma flows from coronal holes quasi-continuously, CIRs/SIRs simultaneously expand and rotate around the Sun, approximately following the Parker spiral shape up to the Earth’s orbit.</p><p>Coronal hole streams rotate not only around the Sun but also around their own axis of simmetry, resembling a screw. This effect may occur because of the following mechanisms: (1) the existence of a difference between the solar wind speed at different sides of the stream, (2) twisting of the magnetic field frozen into the plasma, and  (3) a vortex-like motion of the edge of the mothering coronal hole at the Sun. The screw type of the rotation of a CIR/SIR can lead to centrifugal instability if CIR/SIR inner layers have a larger angular velocity than the outer. Furthermore, the rotational plasma movement and the stream distortion can twist magnetic field lines. The latter contributes to the pinch effect in accordance with a well-known criterion of Suydam instability (Newcomb, 1960, doi: 10.1016/0003-4916(60)90023-3). Owing to the presence of a cylindrical current sheet at the boundary of a coronal hole, conditions for tearing instability can also appear at the CIR/SIR boundary. Regardless of their geometry, large scale current sheets are subject to various instabilities generating plasmoids. Altogether, these effects can lead to the formation of a turbulent region within CIRs/SIRs, making them filled with current sheets and plasmoids. </p><p>We study a substructure of CIRs/SIRs, characteristics of their rotation in the solar wind, and give qualitative estimations of possible mechanisms which lead to splitting of the leading edge a coronal hole flow and consequent formation of current sheets within CIRs/SIRs.</p>

A Lunar-Month Modulation of Large Solar-Terrestrial Disturbances

1967 ◽  
Vol 1 (1) ◽  
pp. 11-12 ◽  
Author(s):  
S. F. Smerd
Keyword(s):  
Solar Flare ◽  
Random Distribution ◽  
Full Moon ◽  
Solar Rotation ◽  
Rotation Period ◽  
Solar Proton ◽  
The Sun ◽  
The Moon ◽  
Unexpected Effect ◽  
Solar Proton Events

Dodson and Hedeman discovered an unexpected effect in the occurrence of solar proton events as revealed by polarcap absorption (PCA). When the 48 events in Bailey’s Catalog of the Principal PCA Events, 1952-1963 are distributed with the phase of the moon there is a gap of several days near full moon; also, many more events occur when the moon waxes than when it wanes. Dodson and Hedeman did not find similar, apparent departures from random distribution either with a mean solar rotation period of 27.3 days or for solar flare events. They concluded that ‘at the present time it is not clear whether the 29.5 day “effect” is related to the sun or the moon or is only a statistical accident’.

Evolution of solar wind flows from the inner corona to 1 AU: constraints provided by SOHO UVCS and SWAN data

2021 ◽  
Author(s):  
Alessandro Bemporad ◽  
Olga Katushkina ◽  
Vladislav Izmodenov ◽  
Dimitra Koutroumpa ◽  
Eric Quemerais
Keyword(s):  
Solar Wind ◽  
Interstellar Medium ◽  
Mass Flux ◽  
Solar Rotation ◽  
Numerical Models ◽  
Rotation Period ◽  
Resonant Scattering ◽  
The Sun ◽  
Hydrogen Distribution ◽  
First Results

<p>The Sun modulates with the solar wind flow the shape of the whole Heliosphere interacting with the surrounding interstellar medium. Recent results from IBEX and INCA experiments, as well as recent measurements from Voyager 1 and 2, demonstrated that this interaction is much more complex and subject to temporal and heliolatitudinal variations than previously thought. These variations could be also related with the evolution of solar wind during its journey through the Heliosphere. Hence, understanding how the solar wind evolves from its acceleration region in the inner corona to the Heliospheric boundaries is very important.</p><p>In this work, SWAN Lyman-α full-sky observations from SOHO are combined for the very first time with measurements acquired in the inner corona by SOHO UVCS and LASCO instruments, to trace the solar wind expansion from the Sun to 1 AU. The solar wind mass flux in the inner corona was derived over one full solar rotation period in 1997, based on LASCO polarized brightness measurements, and on the Doppler dimming technique applied to UVCS Lyman-α emission from neutral H coronal atoms due to resonant scattering of chromospheric radiation. On the other hand, the SWAN Lyman-α emission (due to back-scattering from neutral H atoms in the interstellar medium) was analyzed based on numerical models of the interstellar hydrogen distribution in the heliosphere and the radiation transfer. The SWAN full-sky Lyman-α intensity maps are used for solving of the inverse problem and deriving of the solar wind mass flux at 1 AU from the Sun as a function of heliolatitude. First results from this comparison for a chosen time period in 1997 are described here, and possible future applications for Solar Orbiter data are discussed.</p>

scholarly journals II. Notice of a zone of spots on the sun

1867 ◽  
Vol 15 ◽  
pp. 63-70
Keyword(s):  
Rotation Period ◽  
The Sun ◽  
Black Speck

During the latter half of February and the first half of March, spots of extremely varied character have appeared on the sun, and have been seen with great distinctness, in good observing weather, through the whole or parts of two semi-rotations. On the 13th of February, at 10 h 25 m , four spots were visible on the disk, in the situations marked Z, A, B, C in the diagram No. 1. In that diagram the apparent course of the sun’s equator is marked by the curved line e, and the pole of rotation at P. Thus the four spots indicated for observation being all on the same side of the sun’s equator, and all within the latitude of 10°, constitute a zone of spots. Since that date a fifth spot, D, still in the same zone, has appeared, fol­lowing C. Of these Z was about to disappear; its reappearance was noted, and several remarkable changes in form were observed while it traversed half the disk, till its contraction to a black speck 1000 miles in diameter, after which it was obliterated. The spot B had advanced some distance on the disk, and was followed till the 21st of February, when it approached the edge, with indications of being a shallow concavity. It was not observed to reappear. The spots A and C require longer notice, both on account of their persistence through more than a rotation-period, and because of the remarkable changes which they have undergone. The spot D is now under observation. The spot A, visible from the 4th to the 16th of February, and again reappearing early in March, was solitary, and approximately round, mea­suring, on February 10, about 23,000 miles across the penumbra, and about 8000 across the umbra.

scholarly journals Using Sidereal Rotation Period Expressions to Calculate the Sun’s Rotation Period through Observation of Sunspots

2015 ◽  
Vol 2015 ◽  
pp. 1-4 ◽  
Author(s):  
Tsung-Ching Chen ◽  
Jiann-Shing Lih ◽  
Tien-Tang Chang ◽  
Chih-Hung Yang ◽  
Ming-Chi Lu ◽  
...  
Keyword(s):  
Solar Rotation ◽  
Angular Rate ◽  
Rotation Period ◽  
The Sun ◽  
Statistical Research ◽  
Low Latitudes ◽  
Sidereal Rotation

We utilize sidereal rotation period expressions to calculate the sun’s rotation period via sunspot observation. From the well-known astronomical sites, we collected sunspot diagrams for 14 months, from January 2013 to February 2014, to analyze, compare, and implement statistical research. In addition to acquiring the average angular rate of the movement of sunspots, we found that even the same number of sunspots moved at different angular rates, and generally the life of larger sunspots is longer than 10 days. Therefore the larger sunspots moved around the back of the sun, and a handful of relatively smaller sunspots disappeared within a few days. The results show that the solar rotation period varied with the latitude. However, if we take the average of the sunspots at high and low latitudes, we find that the calculated value is very close to the accredited values.

Active longitudes of the sun: The rotation period and statistical significance

2005 ◽  
Vol 31 (4) ◽  
pp. 280-284 ◽  
Author(s):  
L. L. Kitchatinov ◽  
S. V. Olemskoi
Keyword(s):  
Statistical Significance ◽  
Rotation Period ◽  
The Sun

The relation between the synodic and sidereal rotation period of the Sun

Solar Physics ◽  
1995 ◽  
Vol 159 (2) ◽  
pp. 393-398 ◽  
Author(s):  
D. Roša ◽  
R. Brajša ◽  
B. Vršnak ◽  
H. Wöhl
Keyword(s):  
Rotation Period ◽  
The Sun ◽  
Sidereal Rotation

scholarly journals The Sun Through Time

2020 ◽  
Vol 216 (8) ◽  
Author(s):  
Manuel Güdel
Keyword(s):  
Stellar Wind ◽  
Rotation Period ◽  
High Energy ◽  
Magnetic Activity ◽  
Energy Output ◽  
The Sun ◽  
Stellar Rotation ◽  
Solar Mass ◽  
Rotation Periods ◽  
Rotational Evolution

AbstractMagnetic activity of stars like the Sun evolves in time because of spin-down owing to angular momentum removal by a magnetized stellar wind. These magnetic fields are generated by an internal dynamo driven by convection and differential rotation. Spin-down therefore converges at an age of about 700 Myr for solar-mass stars to values uniquely determined by the stellar mass and age. Before that time, however, rotation periods and their evolution depend on the initial rotation period of a star after it has lost its protostellar/protoplanetary disk. This non-unique rotational evolution implies similar non-unique evolutions for stellar winds and for the stellar high-energy output. I present a summary of evolutionary trends for stellar rotation, stellar wind mass loss and stellar high-energy output based on observations and models.

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