120 research outputs found

    Anomalous flows in a sunspot penumbra

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    High-resolution spectropolarimetric observations of active region NOAA 11271 were obtained with the spectro-polarimeter on board Hinode to analyze the properties of an anomalous flow in the photosphere in a sunspot penumbra. We detect a blue-shifted feature that appeared on the limb-side penumbra of a sunspot and that was present intermittently during the next two hours. It exhibited a maximum blue-shift of 1.6 km/s, an area of 5.2 arcsec^2, and an uninterrupted lifetime of 1 hr. The blue-shifted feature, when present, lies parallel to red-shifts. Both blue and red shifts flank a highly inclined/horizontal magnetic structure that is radially oriented in the penumbra. The low-cadence SP maps reveal changes in size, radial position in the penumbra and line-of-sight velocity of the blue-shifted feature, from one scan to the other. There was an increase of nearly 500 G in the field strength and a marginal reduction in the field inclination of about 10 deg with the onset of the blue-shifts. In the chromosphere, intense, arc-shaped brightenings were observed close to the location of the blue-shifts, that extend from the edge of the umbral core to the penumbra-quiet Sun boundary. The strongest and largest brightenings were observed about 30 min after the strongest blue-shifts were detected at the photosphere. The close spatial proximity of the two phenomenon strongly suggests a causal relationship. The blue-shifted feature represents plasma motion that could be related to a magnetic structure that rises in the solar atmosphere and subsequently reconnects with the ambient chromospheric magnetic field of the sunspot or an inverse Evershed flow, which would be unique in the photosphere. This transient phenomena is presumably related to the dynamic stability of the sunspot because the corresponding umbral core separated two days later at the location of the blue-shifts and fragmented subsequently.Comment: Accepted for publication in A&A: 8 pages, 8 figure

    Formation of a penumbra in a decaying sunspot

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    Context : Penumbrae are an important characteristic of sunspots, whose formation is intricately related to the nature of sub-photospheric magnetic fields. Aims : We study the formation of a penumbra in a decaying sunspot and compare its properties with those seen during the development of a proto-spot. Methods : High-resolution spectropolarimetric observations of active region NOAA 11283 were obtained from the spectro-polarimeter on board Hinode. These were complemented with full-disk filtergrams of continuum intensity, line-of-sight magnetograms, and dopplergrams from the Helioseismic and Magnetic Imager at high cadence. Results : The formation of a penumbra in the decaying sunspot occurs after the coalescence of the sunspot with a magnetic fragment/pore, which initially formed in the quiet Sun close to an emerging flux region. At first, a smaller set of penumbral filaments develop near the location of the merger with very bright penumbral grains with intensities of 1.2 I_QS, upflows of 4 km/s, and a lifetime of 10 hr. During the decay of these filaments, a larger segment of a penumbra forms at the location of the coalescence. These new filaments are characterized by nearly supersonic downflows of 6.5 km/s that change to a regular Evershed flow nearly 3 hr later. Conclusions : The coalescence of the pore with the decaying sunspot provided sufficient magnetic flux for the penumbra to form in the sunspot. The emerging flux region could have played a decisive role in this process because the formation occurred at the location of the merger and not on the opposite side of the sunspot.Comment: Accepted for publication in A&A Letters, 6 pages, 4 figure

    Properties of Umbral Dots from Stray Light Corrected Hinode Filtergrams

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    High resolution blue continuum filtergrams from Hinode are employed to study the umbral fine structure of a regular unipolar sunspot. The removal of scattered light from the images increases the rms contrast by a factor of 1.45 on average. Improvement in image contrast renders identification of short filamentary structures resembling penumbrae that are well separated from the umbra-penumbra boundary and comprise bright filaments/grains flanking dark filaments. Such fine structures were recently detected from ground based telescopes and have now been observed with Hinode. A multi-level tracking algorithm was used to identify umbral dots in both the uncorrected and corrected images and to track them in time. The distribution of the values describing the photometric and geometric properties of umbral dots are more easily affected by the presence of stray light while it is less severe in the case of kinematic properties. Statistically, umbral dots exhibit a peak intensity, effective diameter, lifetime, horizontal speed and a trajectory length of 0.29 I_QS, 272 km, 8.4 min, 0.45 km/s and 221 km respectively. The 2 hr 20 min time sequence depicts several locations where umbral dots tend to appear and disappear repeatedly with various time intervals. The correction for scattered light in the Hinode filtergrams facilitates photometry of umbral fine structure which can be related to results obtained from larger telescopes and numerical simulations.Comment: Accepted for publication in ApJ : 10 pages, 10 figures, 3 table

    Prescription to practice in hypertension: a community experience in central Kerala

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    Background: Control of blood pressure is a global challenge and non-adherence to hypertension medications is a public health concern. Patient, medication and system related factors can contribute to non-adherence. The study was to determine adherence to hypertension medications and to understand the barriers to adherence in an adult group in Pathanamthitta District of Central Kerala.Methods: A cross sectional study was conducted in a community setting in 2016, among 139 adults aged 30 years and above on treatment for hypertension for at least six months. Those with gestational hypertension, those having serious comorbid conditions and those unwilling to participate were excluded. The data sheet included basic demographic information and history related to hypertension. A content validated eight item questionnaire was used to assess reported adherence and scores classified level of adherence as good (8), moderate (6-<8) and poor (<6). The data was analyzed using SPSS. Chi square test of significance and multivariate regression analysis were done. P<0.05 was considered statistically significant.Results: The participants were in the age group 34-91 years, 50.4% belonging to 50-69 years, and 75.5% were females. Adherence to hypertension medications was good in 49.6%, moderate in 31.7% and poor in 18.7%. The most common factors reported to contribute to non-adherence were forgetfulness (70.5%), high cost of medications (51.8%), and symptom-free state (27.3%).Conclusions: Adherence was good in less than half the study participants and poor in almost one-fifth. Forgetfulness and high medication costs were the most commonly reported barriers. These findings highlight the importance of individuals, families and health service, joining hands to tackle the public health problem of non-adherence to hypertension medications
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