1,749 research outputs found
Reconstruction of solar activity for the last millennium using Be data
In a recent paper (Usoskin et al., 2002a), we have reconstructed the
concentration of the cosmogenic Be isotope in ice cores from the
measured sunspot numbers by using physical models for Be production in
the Earth's atmosphere, cosmic ray transport in the heliosphere, and evolution
of the Sun's open magnetic flux. Here we take the opposite route: starting from
the Be concentration measured in ice cores from Antarctica and
Greenland, we invert the models in order to reconstruct the 11-year averaged
sunspot numbers since 850 AD. The inversion method is validated by comparing
the reconstructed sunspot numbers with the directly observed sunspot record
since 1610. The reconstructed sunspot record exhibits a prominent period of
about 600 years, in agreement with earlier observations based on cosmogenic
isotopes. Also, there is evidence for the century scale Gleissberg cycle and a
number of shorter quasi-periodicities whose periods seem to fluctuate in the
millennium time scale. This invalidates the earlier extrapolation of
multi-harmonic representation of sunspot activity over extended time intervals.Comment: Submitted to A&
Solar total and spectral irradiance reconstruction over the last 9000 years
Changes in solar irradiance and in its spectral distribution are among the
main natural drivers of the climate on Earth. However, irradiance measurements
are only available for less than four decades, while assessment of solar
influence on Earth requires much longer records. The aim of this work is to
provide the most up-to-date physics-based reconstruction of the solar total and
spectral irradiance (TSI/SSI) over the last nine millennia. The concentrations
of the cosmogenic isotopes 14C and 10Be in natural archives have been converted
to decadally averaged sunspot numbers through a chain of physics-based models.
TSI and SSI are reconstructed with an updated SATIRE model. Reconstructions are
carried out for each isotope record separately, as well as for their composite.
We present the first ever SSI reconstruction over the last 9000 years from the
individual 14C and 10Be records as well as from their newest composite. The
reconstruction employs physics-based models to describe the involved processes
at each step of the procedure. Irradiance reconstructions based on two
different cosmogenic isotope records, those of 14C and 10Be, agree well with
each other in their long-term trends despite their different geochemical paths
in the atmosphere of Earth. Over the last 9000 years, the reconstructed secular
variability in TSI is of the order of 0.11%, or 1.5 W/m2. After the Maunder
minimum, the reconstruction from the cosmogenic isotopes is consistent with
that from the direct sunspot number observation. Furthermore, over the
nineteenth century, the agreement of irradiance reconstructions using isotope
records with the reconstruction from the sunspot number by Chatzistergos et al.
(2017) is better than that with the reconstruction from the WDC-SILSO series
(Clette et al. 2014), with a lower chi-square-value
Spectroscopic Observations of Propagating Disturbances in a Polar Coronal Hole: Evidence of Slow Magneto-acoustic Waves
We focus on detecting and studying quasi-periodic propagating features that
have been interpreted both in terms of slow magneto-acoustic waves and of high
speed upflows. We analyze long duration spectroscopic observations of the
on-disk part of the south polar coronal hole taken on 1997 February 25 by the
SUMER spectrometer aboard SOHO. We calibrated the velocity with respect to the
off-limb region and obtain time--distance maps in intensity, Doppler velocity
and line width. We also perform a cross correlation analysis on different time
series curves at different latitudes. We study average spectral line profiles
at the roots of propagating disturbances and along the propagating ridges, and
perform a red-blue asymmetry analysis. We find the clear presence of
propagating disturbances in intensity and Doppler velocity with a projected
propagation speed of about km s and a periodicity of
14.5 min. To our knowledge, this is the first simultaneous detection
of propagating disturbances in intensity as well as in Doppler velocity in a
coronal hole. During the propagation, an intensity enhancement is associated
with a blue-shifted Doppler velocity. These disturbances are clearly seen in
intensity also at higher latitudes (i.e. closer to the limb), while
disturbances in Doppler velocity becomes faint there. The spectral line
profiles averaged along the propagating ridges are found to be symmetric, to be
well fitted by a single Gaussian, and have no noticeable red-blue asymmetry.
Based on our analysis, we interpret these disturbances in terms of propagating
slow magneto-acoustic waves.Comment: accepted for publication by A&
Grand minima and maxima of solar activity: New observational constraints
Using a reconstruction of sunspot numbers stretching over multiple millennia,
we analyze the statistics of the occurrence of grand minima and maxima and set
new observational constraints on long-term solar and stellar dynamo models.
We present an updated reconstruction of sunspot number over multiple
millennia, from C data by means of a physics-based model, using an
updated model of the evolution of the solar open magnetic flux. A list of grand
minima and maxima of solar activity is presented for the Holocene (since 9500
BC) and the statistics of both the length of individual events as well as the
waiting time between them are analyzed.
The occurrence of grand minima/maxima is driven not by long-term cyclic
variability, but by a stochastic/chaotic process. The waiting time distribution
of the occurrence of grand minima/maxima deviates from an exponential
distribution, implying that these events tend to cluster together with long
event-free periods between the clusters. Two different types of grand minima
are observed: short (30--90 years) minima of Maunder type and long (110
years) minima of Sp\"orer type, implying that a deterministic behaviour of the
dynamo during a grand minimum defines its length. The duration of grand maxima
follows an exponential distribution, suggesting that the duration of a grand
maximum is determined by a random process.
These results set new observational constraints upon the long-term behaviour
of the solar dynamo.Comment: 10 Figure
Male homosexual behavior among different age groups in captive stump-tailed macaque (Macaca arctoides): socio-sexual or sexually motivated?
The present study aims to determine whether homosexual behavior in stump-tailed macaque males of different age groups were socio-sexual or sexually motivated. Male homosexual encounters were divided into two categories for analysis; manual genital stimulation and actual mounting. Manual genital stimulation in adult males occurred bidirectional, in the context of social affiliations. There was no significant difference between dominant and subordinate partners in terms of genital stimulation performed or received. Mounting was in double foot-clasp position similar to heterosexual encounter. We identified three types of mounts. All types of mounts occurred unidirectional among adult males and mostly occurred in aggressive context. Unique homosexual encounters was observed between ñ-male and ĂÂČ-male where mounting involved anal intromission terminated by ejaculation and occurred only during the mating season after the heterosexual copulation between ĂÂČ-male and estrous female, which was known to be sexually motivated. We examined several socio-sexual explanations for male homosexual mounting, including (1) dominance-assertion (2) tension-regulation (3) reconciliation and (4) practice for heterosexual copulation. Homosexual encounters between adult males interpreted: a strict relationship between dominant individuals mounting subordinate individuals, reconciliation attempted by the subordinate; and the mechanism employed to regulated aggression and reestablished social bond among adult males. Mounting among immature males occurred bidirectional. Five evidences indicated the homosexual mounting between immature males as socio-sexual behavior. The evidences based on: (a) the mating season (b) the same day heterosexual encounter (c) assistance provided by adult male to immature males (d) occurrence in the context of play (e) immature males in homosexual mounting and learning heterosexual mounting with adult females. The male-male homosexuality adds a new dimension in sexual behavior of stump-tailed macaque.Ă
Discovery of kilogauss magnetic fields in three DA white dwarfs
We have detected longitudinal magnetic fields between 2 and 4 kG in three (WD
0446790, WD 1105048, WD 2359434) out of a sample of 12 normal DA white
dwarfs by using optical spectropolarimetry done with the VLT Antu 8 m telescope
equipped with FORS1. With the exception of 40 Eri B (4 kG) these are the first
positive detections of magnetic fields in white dwarfs below 30 kG. Although
suspected, it was not clear whether a significant fraction of white dwarfs
contain magnetic fields at this level. These fields may be explained as fossil
relics from magnetic fields in the main-sequence progenitors considerably
enhanced by magnetic flux conservation during the shrinkage of the core. A
detection rate of 25 % (3/12) may indicate now for the first time that a
substantial fraction of white dwarfs have a weak magnetic field. This result,
if confirmed by future observations, would form a cornerstone for our
understanding on the evolution of stellar magnetic fields.
Keywords: stars: white dwarfs - stars: magnetic fields - stars: individual:
WD0446-790, WD1105-048, WD2359-434Comment: 15 pages, 7 figures, Astronomy and Astrophysics, in pres
Prevalence and risk factors of nocturnal enuresis among school age children in rural areas
Background: The word enuresis is derived from a Greek word (enourein) that means âto void urine.â It can occur either during the day or at night (though some restrict the term to bedwetting that occurs at night). Enuresis can be divided into primary and secondary forms. Aim of current study was to find out the prevalence and underlying its risk factors of nocturnal enuresis in age groups 5 to 12 years in the rural areas of the district. Methods: The study was done during the year 2011-12 among 1258 school children residing in rural areas of Ahmadabad district of Gujarat state by the help of health personnel staff with the cooperation of the teaching staff and all the parents of the children.Results: There were 869 males and 389 females. We found the prevalence of nocturnal enuresis in 11.13% of total subjects. Nocturnal enuresis was more common in males than in females, 91/140 in males and 49/140 in female children.Conclusions: Our findings suggest that nocturnal enuresis is a common problem among school children especially with low income, lower age, family history of enuresis and history of urinary tract infection. Enuresis is a pediatric public health problem and efforts at all levels should be made such as preventive, etiological and curative. The ratio of males to females in this study was 1.86 that is comparable to other data of the same study.
Fan Loops Observed by IRIS, EIS and AIA
A comprehensive study of the physical parameters of active region fan loops
is presented using the observations recorded with the Interface Region Imaging
Spectrometer (IRIS), the EUV Imaging Spectrometer (EIS) on-board Hinode and the
Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager
(HMI) on-board the Solar Dynamics Observatory (SDO). The fan loops emerging
from non-flaring AR~11899 (near the disk-center) on 19th November, 2013 are
clearly discernible in AIA 171~{\AA} images and those obtained in \ion{Fe}{8}
and \ion{Si}{7} images using EIS. Our measurements of electron densities reveal
that the footpoints of these loops are approximately at constant pressure with
electron densities of 10.1 cm at
(\ion{O}{4}), and 8.9 cm at
(\ion{Si}{10}). The electron temperature diagnosed across the fan loops by
means of EM-Loci suggest that at the footpoints, there are two temperature
components at and 5.95, which are picked-up by IRIS lines
and EIS lines respectively. At higher heights, the loops are nearly isothermal
at , that remained constant along the loop. The measurement
of Doppler shift using IRIS lines suggests that the plasma at the footpoints of
these loops is predominantly redshifted by 2-3~km~s in \ion{C}{2},
10-15~km~s in \ion{Si}{4} and 15{--}20~km~s in \ion{O}{4},
reflecting the increase in the speed of downflows with increasing temperature
from to 5.15. These observations can be explained by low
frequency nanoflares or impulsive heating, and provide further important
constraints on the modeling of the dynamics of fan loops.Comment: Accepted for publication in The Astrophysical Journal; 8 Figures, 11
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