Synodic Rotation Period Research Articles

Lightcurves, phase function and pole of the asteroid 22 Kalliope

Photoelectric observations of 22 Kalliope give a synodic rotation period of 4 h 08 m 52 s .1 ± 0 s .4, in very good agreement with the previous value (4 h08 m.8) by Ahmad (1954). The magnitude-phase relation shows an opposition effect, starting near a phase angle of 7° to 8°, as usual. From the V magnitude of the maximum light, an effort was made to find the coordinates of the pole of 22 Kalliope using the method of Sather (1976) for 39 Laetitia, assuming a triaxial ellipsoid. We found λ pole = 215 ± 10° and β pole = 45 ± 15°. From the adopted geometrical albedo þ v = 0.123 (Chapman et al., 1975) the resulting dimensions were roughly 215 × 160 × 130 km 3. The possibility of differences in the projected areas of similar extrema was also investigated.

On some features of Pc5 pulsations at choutuppal (Hyderabad), India.

Morphological features of Pc5 pulsations observed in the earth currents at an equatorial station over nearly 6 years show a dominant maximum in the morning in occurrence hours of the pulsation, like at high and middle latitudes, and a much subdued maximum in the evening; a peak near midnight is also seen as reported from auroral zone stations. A semidiurnal variation in the period of the pulsations with a distinct maximum at the hour close to dawn and a minor maximum around dusk is noticed in all the seasons and the year. Similarity of the semidiurnal variation in the periods between the equatorial station and a high latitude station is in conformity with the theoretical models wherein it was suggested that ULF waves can also be observed away from the resonance region as the compressional evanescent mode. Time series analysis of the parameter, occurrence hours per day, indicates significant signal corresponding to solar synodic rotation period for the years 1970-72. Some significant quasi-stationary periodicities in occurrence hours per day are noticed.

A photometric study of the minor planet 63 Ausonia

Photoelectric observations of the minor planet 63 Ausonia were obtained on 12 nights during the 1976 opposition at the Astronomical Observatory of Torino. A complete lightcurve with two maxima and two minima was observed with a maximum amplitude of 0.47 mag. The synodic period of rotation, never before determined photoelectrically, was found to be 9 h17 m48 s ± 5 s. The absolute magnitude of the primary maximum, V 0(1, 0) = 7.49 mag, and the phase coefficient, β v = 0.035 mag/deg, were deduced by the magnitude-phase relation. Comparison with other observations is briefly discussed and a mean radius is determined from a previous value of the geometric albedo.

Preferred solar wind emitting longitudes on the Sun

During the 11½-year period from July 1964 through December 1975, high- and low-speed solar wind flows originated from preferred solar longitudes. The preferred longitude effect was most pronounced from 1970 onward but was also evident in the years preceding 1970. The most pronounced modulation in average solar wind speed with longitude (approximately 20%) was obtained when it was assumed that the synodic rotation period of the sun is 27.025 days. Some deep internal structure in the sun must ultimately be responsible for these long-lived longitudinal effects, which appear to rotate rigidly with the sun.

A possible rotation period for the minor planet 164 Eva

The minor planet 164 Eva passed through opposition on December 1, 1975 with a magnitude B opp = 11.3 mag. Photoelectric observations at the Observatory of Torino, Italy, were carried out in two nights on Oct. 27/28 and Nov. 11, each with a run of about 3 hr. Two further successful photoelectric observations were carried out at the OHP, France, each with a run of about 6 hr. From all observed parts of the lightcurve a resulting synodic period of rotation of about 27.3 hr can be deduced, with a range of the total amplitude of at least Δm = 0.07 mag. With this period of 27.3 hr the minor planet 164 Eva is one more long period object, falling now between 654 Zelinda ( H. J. Schober, 1975, Astron. Astrophys. 44, 85–89 ) and 139 Juewa ( J. Goguen et al., 1976, Icarus 29, 137–142 ), at the high end in the histogram of the distribution of minor planet rotation periods.

Response of stratospheric circulation at 10 mb to solar activity oscillations resulting from the sun's rotation

Indices, which reflect variations of the zonal geostrophic wind at the 10-mb-surface of the northern hemisphere, are compared with solar activity fluctuations applying methods of statistical frequency analysis. At a frequency corresponding to half the synodic rotation period of the sun, a significant response of the stratospheric circulation to solar activity is found for nearly all latitudes between 10 and 80° N. Considering the detailed coherency spectra it is suggested that a stratospheric “system”, e.g. a high or low pressure belt with an average position near 50° N, oscillates with the synodic period of the solar rotation. The periodic variations are probably modulated by annual, semiannual and 4-monthly oscillations of the solar radiation or of stratospheric quantities. Satellite measurements of the stratospheric radiance (temperature) indicate that the response to solar activity fluctuations resulting in quasiperiodic changes of stratospheric properties with half the rotation period of the sun, is a global phenomenon. DOI: 10.1111/j.2153-3490.1977.tb00707.x

Photographic photometry of the asteroid 1975 RB

An unnumbered asteroid was found on plates taken in September 1975 with the Kvistaberg Schmidt telescope. This article presents the asteroid's derived physical parameters and orbital elements. The amplitudes of the two lightcurves were found to be 0. m3 and the synodic rotation period of the asteroid was determined as 0. d376.

Photometric lightcurves and pole determination of 433 Eros

Fourteen photometric lightcurves of 433 Eros were made at the Astronomical Observatory of Torino during the 1974–75 close passage. The absolute magnitude of the primary maximum (10 m78), the phase coefficient (0.023 mag/degree), the synodic and sidereal period of rotation (0 d.21956 and 0 d.21959, respectively) and the ecliptic coordinates of the pole ( λ = 17°, β = 10°) were deduced.

Long Term Evolution of Solar Sector Structure

The large-scale structure of the solar magnetic field during the past five sunspot cycles (representing by implication a much longer interval of time) has been investigated using the polarity (toward or away from the Sun) of the interplanetary magnetic field as inferred from polar geomagnetic observations. The polarity of the interplanetary magnetic field has previously been shown to be closely related to the polarity (into or out of the Sun) of the large-scale solar magnetic field. It appears that a solar structure with four sectors per rotation persisted through the past five sunspot cycles, with a synodic rotation period near 27.0 days, and a small relative westward drift during the first half of each sunspot cycle and a relative eastward drift during the second half of each cycle. Superposed on this four-sector structure there is another structure with inward field polarity, a width in solar longitude of about 100° and a synodic rotation period of about 28 to 29 days. This 28.5 day structure is usually most prominent during a few years near sunspot maximum. Some preliminary comparisons of these observed solar structures with theoretical considerations are given.

Rotational Characteristics of Coronal Holes

From May 1972 to October 1973, daily measures were obtained of EUV coronal hole areas appearing at the central meridian. Autocorrelations of these coronal hole area time series provide synodic rotation periods which indicate an almost rigid rotation by such features for lag lengths as short as one rotation. The rotation periods of coronal holes at high latitudes best compare with inferred interplanetary field rotation periods.

Variation of the solar atmospheric rotation over the 11 year cycle

The synodic rotation period and power spectra of solar microwave sources are investigated using accurate data in the interval 1956 to 1970. The variation of the approximate 27 day period is obtained over a complete solar cycle and is thought to be a result of the latitude change over the solar cycle of the origins of the radio emissions. High resolution power spectra have also been obtained and revealed the existence of a double peaked line near 160 day period. This line is attributed to changes in either the Eartn's heliographic latitudes or the Earth's inclination to the Earth-Sun line.

Solar rotation as marked by extreme-ultraviolet coronal holes

view Abstract Citations (60) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar rotation as marked by extreme-ultraviolet coronal holes. Wagner, W. J. Abstract Spectroheliograms produced in the light of Fe XV lambda-284 by the Goddard Space Flight Center experiment on OSO-7 are used to determine solar rotational periods for low-emission coronal hole features. From 1972 May to 1973 October, daily measures were obtained of the coronal hole area appearing at the central solar meridian. Autocorrelations of the coronal-hole-area time series in seven latitude zones provide synodic rotation periods which indicate a close to rigid rotation by such features for lag lengths of only one rotation. For latitudes below about 50 deg, both the autocorrelation functions for short-lived coronal holes and analyses of more persistent features over these 18 months suggest a quadrupolar distribution of coronal hole longitudes. Publication: The Astrophysical Journal Pub Date: June 1975 DOI: 10.1086/181832 Bibcode: 1975ApJ...198L.141W Keywords: Autocorrelation; Far Ultraviolet Radiation; Solar Corona; Solar Rotation; Spectroheliographs; Line Spectra; Photosphere; Solar Atmosphere; Solar Magnetic Field; Solar Physics; Solar Physics full text sources ADS |

Long term evolution of solar sector structure

The large-scale structure of the solar magnetic field during the past five sunspot cycles (representing by implication a much longer interval of time) has been investigated using the polarity (toward or away from the Sun) of the interplanetary magnetic field as inferred from polar geomagnetic observations. The polarity of the interplanetary magnetic field has previously been shown to be closely related to the polarity (into or out of the Sun) of the large-scale solar magnetic field. It appears that a solar structure with four sectors per rotation persisted through the past five sunspot cycles with a synodic rotation period near 27.0 days, and a small relative westward drift during the first half of each sunspot cycle and a relative eastward drift during the second half of each cycle. Superposed on this four-sector structure there is another structure with inward field polarity, a width in solar longitude of about 100° and a synodic rotation period of about 28 to 29 days. This 28.5 day structure is usually most prominent during a few years near sunspot maximum. Some preliminary comparisons of these observed solar structures with theoretical considerations are given.

Yearly variation in the synodic rotation period of the Sun

Yearly variation in the synodic rotation period of the Sun

On the spectral study of sunspot number and solar radio flux between 600 and 9400 MHz

The relationship between the solar activity, as represented by sunspot number and the slowly varying component of solar radio emission at frequencies from 600 to 9400 MHz, has been sudied for high solar activity (1957–58), declining phase of moderate solar activity (1961–62) and ascending phase of moderate solar activity (1965–66). Regression and auto-spectrum analyses show that the association of the slowly varying radio emissions with sunspot activity is best around 3750 MHz for high solar activity period, around 2800 MHz for moderate activity during the declining phase and in between 2800 and 3750 MHz for ascending phase of activity. The coherence between radio flux at frequencies from 600 MHz to 9400 MHz was high and free from large fluctuations upto wavelengths as short as 7 days in the year 1961–62. At 9400 MHz, however, it is high and steady for wavelengths in excess of about 15 days. At solar synodic rotation period the phase difference between the sunspot number and the slowly varying component shows little change with the wavelength of the radio emission.

Etude de la rotation rétrograde, en 4 jours, de la couche extérieure nuageuse de Vénus

We review briefly photographic as well as spectrographic observations which have allowed us to prove and confirm the retrograde rotation of about 4 days of the external cloud layer of Venus. Certain configurations visible in ultraviolet light—in particular two spots having the shape of a horizontal Y—seem permanent, and we can establish their cartography. But the observations suggest that highlying clouds cover these configurations from time to time. An examination of the displacement of the equatorial spots during time intervals of several hours furnishes an instantaneous synodic rotation period somewhat larger than 4 days for the permanent spots. The synodic period is shorter for the variable spots. The observations of the periodic return, at the subsolar point, of the equatorial Y shaped configurations, suggest that the mean rotation period of these spots is remarkably constant and almost equal to 4 days. This period increases considerably when the spot latitudes are greater than ±6°. Ephemerides have been calculated for the years to come.

Longitude Distribution of Proton Flares as a Function of Recurrence Period

Abstract : The longitude distribution of the solar flares that produced high-energy protons detected at the earth during the past 11-year sunspot cycle is examined. The synodic rotation period is not confined to be the Carrington period (27.2753 days) which corresponds to the use of heliographic longitude, but instead a range of rotation periods from 25 to 34 days is examined in increments of 0.01 days. It is concluded that the apparent tendency of these proton flares to cluster within one hemisphere of heliographic longitude is not statistically significant. (Author)

An unexpected effect in solar cosmic ray data related to 29.5 days

Data relating to the detection of solar protons in the neighborhood of the earth (1952–1963) and to neutron counts (1958–1963) have been distributed on the basis of the mean synodic solar rotation period, 27.3 days, and the approximate synodic month, 29.5 days. In the latter, apparent departures from random distribution are especially marked. 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.