670 research outputs found
Satellite observations of reconnection between emerging and pre-existing small-scale magnetic fields
We report multi-wavelength ultraviolet observations taken with the IRIS
satellite, concerning the emergence phase in the upper chromosphere and
transition region of an emerging flux region (EFR) embedded in the unipolar
plage of active region NOAA 12529. The photospheric configuration of the EFR is
analyzed in detail benefitting from measurements taken with the
spectropolarimeter aboard the Hinode satellite, when the EFR was fully
developed. In addition, these data are complemented by full-disk, simultaneous
observations of the SDO satellite, relevant to the photosphere and the corona.
In the photosphere, magnetic flux emergence signatures are recognized in the
fuzzy granulation, with dark alignments between the emerging polarities,
cospatial with highly inclined fields. In the upper atmospheric layers, we
identify recurrent brightenings that resemble UV bursts, with counterparts in
all coronal passbands. These occur at the edges of the EFR and in the region of
the arch filament system (AFS) cospatial to the EFR. Jet activity is also found
at chromospheric and coronal levels, near the AFS and the observed brightness
enhancement sites. The analysis of the IRIS line profiles reveals the heating
of dense plasma in the low solar atmosphere and the driving of bi-directional
high-velocity flows with speeds up to 100 km/s at the same locations.
Furthermore, we detect a correlation between the Doppler velocity and line
width of the Si IV 1394 and 1402 \AA{} line profiles in the UV burst pixels and
their skewness. Comparing these findings with previous observations and
numerical models, we suggest evidence of several long-lasting, small-scale
magnetic reconnection episodes between the emerging bipole and the ambient
field. This process leads to the cancellation of a pre-existing photospheric
flux concentration of the plage with the opposite polarity flux patch of the
EFR. [...]Comment: 4 pages, 2 figures, to be published in "Nuovo Cimento C" as
proceeding of the Third Meeting of the Italian Solar and Heliospheric
Communit
Recent insights on the penumbra formation process
Using high-resolution spectropolarimetric data acquired by \textit{IBIS}, as
well as \textit{SDO}/HMI observations, we studied the penumbra formation in AR
NOAA 11490 and in a sample of twelve ARs appeared on the solar disk on 2011 and
2012, which were characterized by -type magnetic field configuration.
The results show that the onset of the classical Evershed flow occurs in a very
short time scale, 1-3 hours. Studying the formation of the first penumbral
sector around the following proto-spot, we found that a stable penumbra forms
in the area facing the opposite polarity, which appears to be co-spatial with
an AFS, i.e. in a flux emergence region, in contrast with the results of
\cite{Schlichenmaier2010} concerning the leading polarity of AR NOAA 11490.
Conversely, analyzing the sample of twelve ARs, we noticed that there is not a
preferred location for the formation of the first penumbral sector. We also
observed before the penumbra formation an inverse Evershed flow, which changes
its sign when the penumbra appears. This confirms the observational evidence
that the appearance of the penumbral filaments is correlated with the
transition from the inverse Evershed to the classical Evershed flow.
Furthermore, the analysis suggests that the time needed to form the penumbra
may be related to the location where the penumbra first appears. New
high-resolution observations, like those that will be provided by the European
Solar Telescope, are expected to increase our understanding of the penumbra
formation process.Comment: 3 pages, 2 figures, to be published in "Nuovo Cimento C" as
proceeding of the Third Meeting of the Italian Solar and Heliospheric
Communit
Restoring process of sunspot penumbra
We describe the disappearance of a sector of sunspot penumbra and its
restoring process observed in the preceding sunspot of active region NOAA
12348. The evolution of the magnetic field and the plasma flows support the
idea that the penumbra forms due to a change of inclination of the magnetic
field of the canopy. Moving magnetic features have been observed during the
disintegration phase of that sector of sunspot penumbra. During the restoring
phase we have not observed any magnetic flux emergence around the sunspot. The
restoring process of the penumbra sector completed in about 72 hours and it was
accompanied by the transition from the counter-Evershed flow to the classical
Evershed flow. The inversion of photospheric spectropolarimetric measurements
taken by IBIS allowed us to reconstruct how the uncombed configuration of the
magnetic field forms during the new settlement of the penumbra, i.e., the
vertical component of the magnetic field seems to be progressively replaced by
some horizontal field lines, corresponding to the intra-spines.Comment: 34 pages, 11 figures, accepted for Ap
Adherence of Mobile App-Based Surveys and Comparison With Traditional Surveys: eCohort Study
BACKGROUND: eCohort studies offer an efficient approach for data collection. However, eCohort studies are challenged by volunteer bias and low adherence. We designed an eCohort embedded in the Framingham Heart Study (eFHS) to address these challenges and to compare the digital data to traditional data collection.
OBJECTIVE: The aim of this study was to evaluate adherence of the eFHS app-based surveys deployed at baseline (time of enrollment in the eCohort) and every 3 months up to 1 year, and to compare baseline digital surveys with surveys collected at the research center.
METHODS: We defined adherence rates as the proportion of participants who completed at least one survey at a given 3-month period and computed adherence rates for each 3-month period. To evaluate agreement, we compared several baseline measures obtained in the eFHS app survey to those obtained at the in-person research center exam using the concordance correlation coefficient (CCC).
RESULTS: Among the 1948 eFHS participants (mean age 53, SD 9 years; 57% women), we found high adherence to baseline surveys (89%) and a decrease in adherence over time (58% at 3 months, 52% at 6 months, 41% at 9 months, and 40% at 12 months). eFHS participants who returned surveys were more likely to be women (adjusted odds ratio [aOR] 1.58, 95% CI 1.18-2.11) and less likely to be smokers (aOR 0.53, 95% CI 0.32-0.90). Compared to in-person exam data, we observed moderate agreement for baseline app-based surveys of the Physical Activity Index (mean difference 2.27, CCC=0.56), and high agreement for average drinks per week (mean difference 0.54, CCC=0.82) and depressive symptoms scores (mean difference 0.03, CCC=0.77).
CONCLUSIONS: We observed that eFHS participants had a high survey return at baseline and each 3-month survey period over the 12 months of follow up. We observed moderate to high agreement between digital and research center measures for several types of surveys, including physical activity, depressive symptoms, and alcohol use. Thus, this digital data collection mechanism is a promising tool to collect data related to cardiovascular disease and its risk factors
Height dependence of the penumbral fine-scale structure in the inner solar atmosphere
We studied the physical parameters of the penumbra in a large and
fully-developed sunspot, one of the largest over the last two solar cycles, by
using full-Stokes measurements taken at the photospheric Fe I 617.3 nm and
chromospheric Ca II 854.2 nm lines with the Interferometric Bidimensional
Spectrometer. Inverting measurements with the NICOLE code, we obtained the
three-dimensional structure of the magnetic field in the penumbra from the
bottom of the photosphere up to the middle chromosphere. We analyzed the
azimuthal and vertical gradient of the magnetic field strength and inclination.
Our results provide new insights on the properties of the penumbral magnetic
fields in the chromosphere at atmospheric heights unexplored in previous
studies. We found signatures of the small-scale spine and intra-spine structure
of both the magnetic field strength and inclination at all investigated
atmospheric heights. In particular, we report typical peak-to-peak variations
of the field strength and inclination of G and , respectively, in the photosphere, and of G and
in the chromosphere. Besides, we estimated the vertical
gradient of the magnetic field strength in the studied penumbra: we find a
value of G km between the photosphere and the middle
chromosphere. Interestingly, the photospheric magnetic field gradient changes
sign from negative in the inner to positive in the outer penumbra.Comment: 14 page, 9 figures, accepted for Ap
Recommended from our members
Depressive symptoms are associated with visceral adiposity in a community-based sample of middle-aged women and men
To examine the relation between measures of adiposity and depressive symptoms in a large well characterized community-based sample, we examined the relations of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) to depressive symptoms in 1581 women (mean age 52.2 years) and 1718 men (mean age 49.8 years) in the Framingham Heart Study. Depressive symptoms were measured using the Center for Epidemiologic Studies Depression (CES-D) scale. Regression models were created to examine the association between each fat depot (exposure) and depressive symptoms (outcome). Sex specific models were adjusted for age, body mass index, smoking, alcohol consumption, diabetes, hypertension, total and HDL cholesterol, lipid lowering treatment, CVD, menopause, C-reactive protein, and physical activity. Mean CES-D scores were 6.8 and 5.6 in women and men. High levels of depressive symptoms were present in 22.5% of women and 12.3% of men. In women, one standard deviation increase in VAT was associated with a 1.3 point higher CES-D score after adjusting for age and BMI (p<0.01) and remained significant in the fully adjusted model (p=0.03). The odds ratio of depressive symptoms per 1 standard deviation increase in VAT in women was 1.33 (p=0.015); results were attenuated in fully adjusted models (OR 1.29, p=0.055). In men, the association between VAT and CES-D score and depressive symptoms was not significant. SAT was not associated with CES-D score or depressive symptoms. This study supports an association between VAT and depressive symptoms in women. Further work is needed to uncover the complex biologic mechanisms mediating the association
- …