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

Solar Physics ◽  
1996 ◽  
Vol 168 (1) ◽  
pp. 211-213 ◽  
Author(s):  
Axel D. Wittmann
Keyword(s):  
Rotation Period ◽  
The Sun ◽  
Sidereal Rotation

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.

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 Reconstruction of asteroid spin states from Gaia DR2 photometry

2018 ◽  
Vol 620 ◽  
pp. A91 ◽  
Author(s):  
J. Ďurech ◽  
J. Hanuš
Keyword(s):  
Rotation Period ◽  
Inversion Method ◽  
Triaxial Ellipsoid ◽  
Independent Data ◽  
Rotation Periods ◽  
Shape Models ◽  
Pole Parameter ◽  
Data Points ◽  
Sidereal Rotation ◽  
Gaia Dr2

Context. In addition to stellar data, Gaia Data Release 2 (DR2) also contains accurate astrometry and photometry of about 14 000 asteroids covering 22 months of observations. Aims. We used Gaia asteroid photometry to reconstruct rotation periods, spin axis directions, and the coarse shapes of a subset of asteroids with enough observations. One of our aims was to test the reliability of the models with respect to the number of data points and to check the consistency of these models with independent data. Another aim was to produce new asteroid models to enlarge the sample of asteroids with known spin and shape. Methods. We used the lightcurve inversion method to scan the period and pole parameter space to create final shape models that best reproduce the observed data. To search for the sidereal rotation period, we also used a simpler model of a geometrically scattering triaxial ellipsoid. Results. By processing about 5400 asteroids with at least 10 observations in DR2, we derived models for 173 asteroids, 129 of which are new. Models of the remaining asteroids were already known from the inversion of independent data, and we used them for verification and error estimation. We also compared the formally best rotation periods based on Gaia data with those derived from dense lightcurves. Conclusions. We show that a correct rotation period can be determined even when the number of observations N is less than 20, but the rate of false solutions is high. For N > 30, the solution of the inverse problem is often successful and the parameters are likely to be correct in most cases. These results are very promising because the final Gaia catalogue should contain photometry for hundreds of thousands of asteroids, typically with several tens of data points per object, which should be sufficient for reliable spin reconstruction.

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 Solar activity and differential rotation

2010 ◽  
Vol 6 (S273) ◽  
pp. 298-302
Author(s):  
Hari Om Vats ◽  
Satish Chandra
Keyword(s):  
Solar Activity ◽  
Differential Rotation ◽  
Rotation Rate ◽  
Rotation Period ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
X Ray ◽  
Sunspot Numbers ◽  
Sidereal Rotation

AbstractThe coronal sidereal rotation rate as a function of latitude for each year, extending from 1992 to 2001 for soft X-ray images and from 1998 - 2005 for radio images are obtained. The present analysis reveals that the equatorial rotation rate of the corona is comparable to the photosphere and the chromosphere, However, at the higher latitudes, the corona rotation quite differently than the photosphere and chromosphere. The latitude differential obtained by both radio and X-ray images is quite variable throughout the period of the study. The equatorial rotation period seems to vary almost systematically with sunspot numbers which indicates its dependence on the phases of the solar activity cycle.

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.

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