1,117 research outputs found
Sunspot areas and tilt angles for solar cycles 7-10
Extending the knowledge about the properties of solar cycles into the past is
essential for understanding the solar dynamo. This paper aims at estimating
areas of sunspots observed by Schwabe in 1825-1867 and at calculating the tilt
angles of sunspot groups. The sunspot sizes in Schwabe's drawings are not to
scale and need to be converted into physical sunspot areas. We employed a
statistical approach assuming that the area distribution of sunspots was the
same in the 19th century as it was in the 20th century. Umbral areas for about
130,000 sunspots observed by Schwabe were obtained, as well as the tilt angles
of sunspot groups assuming them to be bipolar. There is, of course, no polarity
information in the observations. The annually averaged sunspot areas correlate
reasonably with sunspot number. We derived an average tilt angle by attempting
to exclude unipolar groups with a minimum separation of the two alleged
polarities and an outlier rejection method which follows the evolution of each
group and detects the moment it turns unipolar at its decay. As a result, the
tilt angles, although displaying considerable scatter, place the leading
polarity on average 5.85+-0.25 closer to the equator, in good agreement with
tilt angles obtained from 20th-century data sets. Sources of uncertainties in
the tilt angle determination are discussed and need to be addressed whenever
different data sets are combined. The sunspot area and tilt angle data are
provided online.Comment: accepted for publication in Astron. & Astrophy
Temporal relation between quiet-Sun transverse fields and the strong flows detected by IMaX/SUNRISE
Localized strongly Doppler-shifted Stokes V signals were detected by
IMaX/SUNRISE. These signals are related to newly emerged magnetic loops that
are observed as linear polarization features. We aim to set constraints on the
physical nature and causes of these highly Doppler-shifted signals. In
particular, the temporal relation between the appearance of transverse fields
and the strong Doppler shifts is analyzed in some detail. We calculated the
time difference between the appearance of the strong flows and the linear
polarization. We also obtained the distances from the center of various
features to the nearest neutral lines and whether they overlap or not. These
distances were compared with those obtained from randomly distributed points on
observed magnetograms. Various cases of strong flows are described in some
detail. The linear polarization signals precede the appearance of the strong
flows by on average 84+-11 seconds. The strongly Doppler-shifted signals are
closer (0.19") to magnetic neutral lines than randomly distributed points
(0.5"). Eighty percent of the strongly Doppler-shifted signals are close to a
neutral line that is located between the emerging field and pre-existing
fields. That the remaining 20% do not show a close-by pre-existing field could
be explained by a lack of sensitivity or an unfavorable geometry of the
pre-existing field, for instance, a canopy-like structure. Transverse fields
occurred before the observation of the strong Doppler shifts. The process is
most naturally explained as the emergence of a granular-scale loop that first
gives rise to the linear polarization signals, interacts with pre-existing
fields (generating new neutral line configurations), and produces the observed
strong flows. This explanation is indicative of frequent small-scale
reconnection events in the quiet Sun.Comment: 11 pages, 8 figure
On the intensity contrast of solar photospheric faculae and network elements
Sunspots, faculae and the magnetic network contribute to solar irradiance
variations. The contribution due to faculae and the network is of basic
importance, but suffers from considerable uncertainty. We determine the
contrasts of active region faculae and the network, both as a function of
heliocentric angle and magnetogram signal. To achieve this, we analyze
near-simultaneous full disk images of photospheric continuum intensity and
line-of-sight magnetic field provided by the Michelson Doppler Interferometer
(MDI) on board the SOHO spacecraft. Starting from the surface distribution of
the solar magnetic field we first construct a mask, which is then used to
determine the brightness of magnetic features, and the relatively field-free
part of the photosphere separately. By sorting the magnetogram signal into
different bins we are able to distinguish between the contrasts of different
concentrations of magnetic field. We find that the contrasts of active region
faculae (large magnetogram signal) and the network (small signal) exhibit a
very different CLV, showing that the populations of magnetic flux tubes are
different. This implies that these elements need to be treated separately when
reconstructing variations of the total solar irradiance with high precision. We
have obtained an analytical expression for the contrast of photospheric
magnetic features as a function of both position on the disk and magnetic field
strength, by performing a 2-dimensional fit to the observations.Comment: 12 pages, 8 figures, uses aa.cl
Comparison of solar photospheric bright points between SUNRISE observations and MHD simulations
Bright points (BPs) in the solar photosphere are radiative signatures of
magnetic elements described by slender flux tubes located in the darker
intergranular lanes. They contribute to the ultraviolet (UV) flux variations
over the solar cycle and hence may influence the Earth's climate. Here we
combine high-resolution UV and spectro-polarimetric observations of BPs by the
SUNRISE observatory with 3D radiation MHD simulations. Full spectral line
syntheses are performed with the MHD data and a careful degradation is applied
to take into account all relevant instrumental effects of the observations. It
is demonstrated that the MHD simulations reproduce the measured distributions
of intensity at multiple wavelengths, line-of-sight velocity, spectral line
width, and polarization degree rather well. Furthermore, the properties of
observed BPs are compared with synthetic ones. These match also relatively
well, except that the observations display a tail of large and strongly
polarized BPs not found in the simulations. The higher spatial resolution of
the simulations has a significant effect, leading to smaller and more numerous
BPs. The observation that most BPs are weakly polarized is explained mainly by
the spatial degradation, the stray light contamination, and the temperature
sensitivity of the Fe I line at 5250.2 \AA{}. The Stokes asymmetries of the
BPs increase with the distance to their center in both observations and
simulations, consistent with the classical picture of a production of the
asymmetry in the canopy. This is the first time that this has been found also
in the internetwork. Almost vertical kilo-Gauss fields are found for 98 % of
the synthetic BPs. At the continuum formation height, the simulated BPs are on
average 190 K hotter than the mean quiet Sun, their mean BP field strength is
1750 G, supporting the flux-tube paradigm to describe BPs.Comment: Accepted for publication in Astronomy & Astrophysics on May 30 201
Are there field-free gaps near tau=1 in sunspot penumbrae?
The vertical stratification of the magnetic field strength in sunspot
penumbrae is investigated by means of spectropolarimetric observations at high
spatial resolution from the Hinode spacecraft. Assuming that the magnetic field
changes linearly with optical depth we find that, in those regions where the
magnetic field is more inclined and the Evershed flow is strongest (penumbral
intraspines), the magnetic field can either increase or decrease with depth.
Allowing more degrees of freedom to the magnetic field stratification reveals
that the magnetic field initially decreases from \log\tau_5 = -3 until
\log\tau_5 \simeq -1.0, but increases again below that. The presence of strong
magnetic fields near the continuum is at odds with the existence of regions
void of magnetic fields at, or right below, the \tau_5=1 level in the penumbra.
However, they are compatible with the presence of a horizontal flux-tube-like
field embedded in a magnetic atmosphere.Comment: 10 pages, 11 figures (3 color figures, f2,f3,f5,f10,f11 low
resolution). Accepted for publication in ApJ. To appear in issue 1, vol 686,
October 200
A study of prevalence of Sexually Transmitted Infections & response to syndromic treatment among married women of reproductive age group in rural area of Parol Primary Health Centre under Thane district
Objectives To study prevalence of Sexually Transmitted Infections (STIs - symptomatic, clinical & laboratorial)& response to syndromic treatment in among STI groups. Design Community based interventional study Setting Rual area-Parol Primary Health Centre(PHC), District Thane, Maharashtra state. Poulation Women of reproductive age groups 15 -45 years Methods Present Community based interventional study was conducted among representative group of 415 women of reproductive age groups who were selected by simple random sampling technique in Parol PHC, District Thane, Maharashtra state. All symptomatic & asymptomatic women were counseled for examination & investigations & given syndromic treatment. Follow-up done to assess impact of syndromic treatment. Main Outcome Prevalence of STI symptomatically was 39%, clinically 32.3% & Laboratorial 26%. After syndromic treatment, prevalence of STIs was significantly reduced. Statistical Analysis Z test Results Of the surveyed women (415), prevalence of STI symptomatically was 39%, clinically 32.3% & Laboratorial 26%. The most common presenting symptom was vaginal discharge (36.4%) followed by Burning Micturition (24.7%), Vulval itching (17.3%), Lower abdominal pain (13%) & Genital ulcer (8.6%). Clinically, 55.2% women were diagnosed as cervicitis & 44.8% as PID. Laboratorial diagnosed STIs were - vaginal candidiasis 46.3%, Bacterial vaginosis 25%, Trichmoniasis 19.4 %, Genital Herpes 7.4% & HIV 1.9%. After syndromic treatment, prevalence of STIs has statistically significantly reduced. Conclusion Syndromic Rx & health education can definitely reduce STIs
Influence of phase-diversity image reconstruction techniques on circular polarization asymmetries
Full Stokes filter-polarimeters are key instruments for investigating the
rapid evolution of magnetic structures on the solar surface. To this end, the
image quality is routinely improved using a-posteriori image reconstruction
methods. We analyze the robustness of circular polarization asymmetries to
phase-diversity image reconstruction techniques. We use snapshots of
magneto-hydrodynamical simulations carried out with different initial
conditions to synthesize spectra of the magnetically sensitive Fe I line at
5250.2 A. We degrade the synthetic profiles spatially and spectrally to
simulate observations with the IMaX full Stokes filter-polarimeter. We also
simulate the focused/defocused pairs of images used by the phase-diversity
algorithm for reconstruction and the polarimetric modulation scheme. We assume
that standard optimization methods are able to infer the projection of the
wavefront on the Zernike polynomials with 10% precision. We also consider the
less favorable case of 25% precision. We obtain reconstructed monochromatic
modulated images that are later demodulated and compared with the original
maps. Although asymmetries are often difficult to define in the quiet Sun due
to the complexity of the Stokes V profiles, we show how asymmetries are
degraded with spatial and spectral smearing. The results indicate that,
although image reconstruction techniques reduce the spatial smearing, they can
modify the asymmetries of the profiles, mainly caused by the appearance of
spatially-correlated noise.Comment: 10 pages, accepted for publication in A&
First evidence of interaction between longitudinal and transverse waves in solar magnetic elements
Small-scale magnetic fields are thought to play an important role in the
heating of the outer solar atmosphere. By taking advantage of the unprecedented
high-spatial and temporal cadence of IMaX, the filter vector polarimeter on
board the Sunrise balloon-borne observatory, we study the transversal and
longitudinal velocity oscillations in small magnetic elements. The results of
this analysis are then compared to MHD simulations, showing excellent
agreement. We found buffeting-induced transverse oscillations with velocity
amplitudes of the order of 1-2 km/s, to be common along with longitudinal
oscillations with amplitudes 0.4 km/s. Moreover, we also found an interaction
between transverse oscillations and longitudinal velocity oscillations, showing
a +-90 degrees phase lag at the frequency at which they exhibit the maximum
coherence in the power spectrum. Our results are consistent with the
theoretical picture in which MHD longitudinal waves are excited inside small
magnetic elements as a response of the flux tube to the forcing action of the
granular flows.Comment: 9 pages, 7 figures, A&A accepte
First polarimetric observations and modeling of the FeH F^4 Delta-X^4 Delta system
Lines of diatomic molecules are more temperature and pressure sensitive than
atomic lines, which makes them ideal tools for studying cool stellar
atmospheres an internal structure of sunspots and starspots. The FeH F^4
Delta-X^4 Delta system represents such an example that exhibits in addition a
large magnetic field sensitivity. The current theoretical descriptions of these
transitions including the molecular constants involved are only based on
intensity measurements because polarimetric observations have not been
available so far, which limits their diagnostic value. We present for the first
time spectropolarimetric observations of the FeH F^4 Delta-X^4 Delta system
measured in sunspots to investigate their diagnostic capabilities for probing
solar and stellar magnetic fields. We investigate whether the current
theoretical model of FeH can reproduce the observed Stokes profiles including
their magnetic properties. The polarimetric observations are compared with
synthetic Stokes profiles modeled with radiative transfer calculations. This
allows us to infer the temperature and the magnetic field strength of the
observed sunspots. We find that the current theory successfully reproduces the
magnetic properties of a large number of lines in the FeH F^4 Delta-X^4 Delta
system. In a few cases the observations indicate a larger Zeeman splitting than
predicted by the theory. There, our observations have provided additional
constraints, which allowed us to determine empirical molecular constants. The
FeH F^4 Delta-X^4 Delta system is found to be a very sensitive magnetic
diagnostic tool. Polarimetric data of these lines provide us with more direct
information to study the coolest parts of astrophysical objects.Comment: 4 pages, 3 figure
Surface waves in solar granulation observed with {\sc Sunrise}
Solar oscillations are expected to be excited by turbulent flows in the
intergranular lanes near the solar surface. Time series recorded by the IMaX
instrument aboard the {\sc Sunrise} observatory reveal solar oscillations at
high resolution, which allow studying the properties of oscillations with short
wavelengths. We analyze two times series with synchronous recordings of Doppler
velocity and continuum intensity images with durations of 32\thinspace min and
23\thinspace min, resp., recorded close to the disk center of the Sun to study
the propagation and excitation of solar acoustic oscillations. In the Doppler
velocity data, both the standing acoustic waves and the short-lived,
high-degree running waves are visible. The standing waves are visible as
temporary enhancements of the amplitudes of the large-scale velocity field due
to the stochastic superposition of the acoustic waves. We focus on the
high-degree small-scale waves by suitable filtering in the Fourier domain.
Investigating the propagation and excitation of - and -modes with wave
numbers \thinspace 1/Mm we find that also exploding granules
contribute to the excitation of solar -modes in addition to the contribution
of intergranular lanes.Comment: 12 pages, 4 figures, to appear in a special volume on Sunrise in
Astrophysical Journal Letter
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