The Fine-Structure of the Net-Circular Polarization in a Sunspot Penumbra

We present novel evidence for a fine structure observed in the net-circular polarization (NCP) of a sunspot penumbra based on spectropolarimetric measurements utilizing the Zeeman sensitive FeI 630.2 nm line. For the first time we detect a filamentary organized fine structure of the NCP on spatial scales that are similar to the inhomogeneities found in the penumbral flow field. We also observe an additional property of the visible NCP, a zero-crossing of the NCP in the outer parts of the center-side penumbra, which has not been recognized before. In order to interprete the observations we solve the radiative transfer equations for polarized light in a model penumbra with embedded magnetic flux tubes. We demonstrate that the observed zero-crossing of the NCP can be explained by an increased magnetic field strength inside magnetic flux tubes in the outer penumbra combined with a decreased magnetic field strength in the background field. Our results strongly support the concept of the uncombed penumbra

Spatial Relationship between Solar Flares and Coronal Mass Ejections

We report on the spatial relationship between solar flares and coronal mass ejections (CMEs) observed during 1996-2005 inclusive. We identified 496 flare-CME pairs considering limb flares (distance from central meridian > 45 deg) with soft X-ray flare size > C3 level. The CMEs were detected by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). We investigated the flare positions with respect to the CME span for the events with X-class, M-class, and C-class flares separately. It is found that the most frequent flare site is at the center of the CME span for all the three classes, but that frequency is different for the different classes. Many X-class flares often lie at the center of the associated CME, while C-class flares widely spread to the outside of the CME span. The former is different from previous studies, which concluded that no preferred flare site exists. We compared our result with the previous studies and conclude that the long-term LASCO observation enabled us to obtain the detailed spatial relation between flares and CMEs. Our finding calls for a closer flare-CME relationship and supports eruption models typified by the CSHKP magnetic reconnection model.Comment: 7 pages; 4 figures; Accepted by the Astrophysical Journa

ANALISIS KADAR NITROGEN PUPUK ORGANIK CAIR LIMBAH KULIT KAKAO DAN TANDAN KOSONG KELAPA SAWIT DENGAN STARTER EM-4

Penelitian ini bertujuan untuk mengetahui kadar Nitrogen yang terkandung pada pupuk organik cair limbah kulit kakao dan tandan kosong kelapa sawit dengan starter EM-4. Pada penelitian ini terdapat 3 perlakuan perbandingan limbah kulit kakao dan tandan kosong kelapa sawit, yaitu: P1 (1:1), P2 (2:1) dan P3 (1:2). Pengujian kadar Nitrogen menggunakan metode kjeldhal. Berdasarkan hasil pengujian yang dilakukan, kadar N-total dari pupuk organik cair dari limbah kulit kakao dan tandan kosong kelapa sawit dalah P1 sebesar 0,87%, P2 0,82% dan P3 0,65%

A new look at a polar crown cavity as observed by SDO/AIA

Context. The Solar Dynamics Observatory (SDO) was launched in February 2010 and is now providing an unprecedented view of the solar activity at high spatial resolution and high cadence covering a broad range of temperature layers of the atmosphere. Aims. We aim at defining the structure of a polar crown cavity and describing its evolution during the erupting process. Methods. We use the high-cadence time series of SDO/AIA observations at 304 Å (50 000 K) and 171 Å (0.6 MK) to determine the structure of the polar crown cavity and its associated plasma, as well as the evolution of the cavity during the different phases of the eruption. We report on the observations recorded on 13 June 2010 located on the north-west limb. Results. We observe coronal plasma shaped by magnetic field lines with a negative curvature (U-shape) sitting at the bottom of a cavity. The cavity is located just above the polar crown filament material. We thus observe the inner part of the cavity above the filament as depicted in the classical three part coronal mass ejection (CME) model composed of a filament, a cavity, and a CME front. The filament (in this case a polar crown filament) is part of the cavity, and it makes a continuous structuring from the filament to the CME front depicted by concentric ellipses (in a 2D cartoon). Conclusions. We propose to define a polar crown cavity as a density depletion sitting above denser polar crown filament plasma drained down the cavity by gravity. As part of the polar crown filament, plasma at different temperatures (ranging from 50 000 K to 0.6 MK) is observed at the same location on the cavity dips and sustained by a competition between the gravity and the curvature of magnetic field lines. The eruption of the polar crown cavity as a solid body can be decomposed into two phases: a slow rise at a speed of 0.6 km s-1 and an acceleration phase at a mean speed of 25 km s-1

On the Doppler Shift and Asymmetry of Stokes Profiles of Photospheric FeI and Chromospheric MgI Lines

We analyzed the full Stokes spectra using simultaneous measurements of the photospheric (FeI 630.15 and 630.25 nm) and chromospheric (MgI b2 517.27 nm) lines. The data were obtained with the HAO/NSO Advanced Stokes Polarimeter, about a near disc center sunspot region, NOAA AR 9661. We compare the characteristics of Stokes profiles in terms of Doppler shifts and asymmetries among the three spectral lines, which helps us to better understand the chromospheric lines and the magnetic and flow fields in different magnetic regions. The main results are: (1) For penumbral area observed by the photospheric FeI lines, Doppler velocities derived from Stokes I (Vi) are very close to those derived from linear polarization profiles (Vlp) but significantly different from those derived from Stokes V profiles (Vzc), which provides direct and strong evidence that the penumbral Evershed flows are magnetized and mainly carried by the horizontal magnetic component. (2) The rudimentary inverse Evershed effect observed by the MgI b2 line provides a qualitative evidence on its formation height that is around or just above the temperature minimum region. (3) Vzc and Vlp in penumbrae and Vzc in pores generally approach their Vi observed by the chromospheric MgI line, which is not the case for the photospheric FeI lines. (4) Outer penumbrae and pores show similar behavior of the Stokes V asymmetries that tend to change from positive values in the photosphere (FeI lines) to negative values in the low chromosphere (MgI line). (5) The Stokes V profiles in plage regions are highly asymmetric in the photosphere and more symmetric in the low chromosphere. (6) Strong red shifts and large asymmetries are found around the magnetic polarity inversion line within the common penumbra of the Delta spot. This study thus emphasizes the importance of spectro-polarimetry using chromospheric lines.Comment: 10 pages, 7 figures, accepted to The Astrophysical Journa

Habitat complexity and predator odours impact on the stress response and antipredation behaviour in coral reef fish

Mass coral bleaching events coupled with local stressors have caused regional-scale loss of corals on reefs globally. Following the loss of corals, the structural complexity of these habitats is often reduced. By providing shelter, obscuring visual information, or physically impeding predators, habitat complexity can influence predation risk and the perception of risk by prey. Yet little is known on how habitat complexity and risk assessment interact to influence predator-prey interactions. To better understand how prey’s perception of threats may shift in degraded ecosystems, we reared juvenile Pomacentrus chrysurus in environments of various habitat complexity levels and then exposed them to olfactory risk odours before simulating a predator strike. We found that the fast-start escape responses were enhanced when forewarned with olfactory cues of a predator and in environments of increasing complexity. However, no interaction between complexity and olfactory cues was observed in escape responses. To ascertain if the mechanisms used to modify these escape responses were facilitated through hormonal pathways, we conducted whole-body cortisol analysis. Cortisol concentrations interacted with habitat complexity and risk odours, such that P. chrysurus exhibited elevated cortisol levels when forewarned with predator odours, but only when complexity levels were low. Our study suggests that as complexity is lost, prey may more appropriately assess predation risk, likely as a result of receiving additional visual information. Prey’s ability to modify their responses depending on the environmental context suggests that they may be able to partly alleviate the risk of increased predator-prey interactions as structural complexity is reduced

Fluxtube model atmospheres and Stokes V zero-crossing wavelengths

First results of the inversion of Stokes I and V profiles from plage regions near disk center are presented. Both low and high spatial resolution spectra of FeI 6301.5 and FeI 6302.5 A obtained with the Advanced Stokes Polarimeter (ASP) have been considered for analysis. The thin flux tube approximation, implemented in an LTE inversion code based on response functions, is used to describe unresolved magnetic elements. The code allows the simultaneous and consistent inference of all atmospheric quantities determining the radiative transfer with the sole assumption of hydrostatic equilibrium. By considering velocity gradients within the tubes we are able to match the full ASP Stokes profiles. The magnetic atmospheres derived from the inversion are characterized by the absence of significant motions in high layers and strong velocity gradients in deeper layers. These are essential to reproduce the asymmetries of the observed profiles. Our scenario predicts a shift of the Stokes V zero-crossing wavelengths which is indeed present in observations made with the Fourier Transform Spectrometer.Comment: To appear in ApJ Letters (1997) (in press

Experiments with a Malkus-Lorenz water wheel: Chaos and Synchronization

We describe a simple experimental implementation of the Malkus-Lorenz water wheel. We demonstrate that both chaotic and periodic behavior is found as wheel parameters are changed in agreement with predictions from the Lorenz model. We furthermore show that when the measured angular velocity of our water wheel is used as an input signal to a computer model implementing the Lorenz equations, high quality chaos synchronization of the model and the water wheel is achieved. This indicates that the Lorenz equations provide a good description of the water wheel dynamics.Comment: 12 pages, 7 figures. The following article has been accepted by the American Journal of Physics. After it is published, it will be found at http://scitation.aip.org/ajp

Self-Consistent MHD Modeling of a Coronal Mass Ejection, Coronal Dimming, and a Giant Cusp-Shaped Arcade Formation

We performed magnetohydrodynamic simulation of coronal mass ejections (CMEs) and associated giant arcade formations, and the results suggested new interpretations of observations of CMEs. We performed two cases of the simulation: with and without heat conduction. Comparing between the results of the two cases, we found that reconnection rate in the conductive case is a little higher than that in the adiabatic case and the temperature of the loop top is consistent with the theoretical value predicted by the Yokoyama-Shibata scaling law. The dynamical properties such as velocity and magnetic fields are similar in the two cases, whereas thermal properties such as temperature and density are very different.In both cases, slow shocks associated with magnetic reconnectionpropagate from the reconnection region along the magnetic field lines around the flux rope, and the shock fronts form spiral patterns. Just outside the slow shocks, the plasma density decreased a great deal. The soft X-ray images synthesized from the numerical results are compared with the soft X-ray images of a giant arcade observed with the Soft X-ray Telescope aboard {\it Yohkoh}, it is confirmed that the effect of heat conduction is significant for the detailed comparison between simulation and observation. The comparison between synthesized and observed soft X-ray images provides new interpretations of various features associated with CMEs and giant arcades.Comment: 39 pages, 18 figures. Accepted for publication in the Astrophysical Journal. The PDF file with high resplution figures can be downloaded from http://www.kwasan.kyoto-u.ac.jp/~shiota/study/ApJ62426.preprint.pdf

Correlations of Online Search Engine Trends with Coronavirus Disease (COVID-19) Incidence: Infodemiology Study

Background: The coronavirus disease (COVID-19) is the latest pandemic of the digital age. With the internet harvesting large amounts of data from the general population in real time, public databases such as Google Trends (GT) and the Baidu Index (BI) can be an expedient tool to assist public health efforts. Objective: The aim of this study is to apply digital epidemiology to the current COVID-19 pandemic to determine the utility of providing adjunctive epidemiologic information on outbreaks of this disease and evaluate this methodology in the case of future pandemics. Methods: An epidemiologic time series analysis of online search trends relating to the COVID-19 pandemic was performed from January 9, 2020, to April 6, 2020. BI was used to obtain online search data for China, while GT was used for worldwide data, the countries of Italy and Spain, and the US states of New York and Washington. These data were compared to real-world confirmed cases and deaths of COVID-19. Chronologic patterns were assessed in relation to disease patterns, significant events, and media reports. Results: Worldwide search terms for shortness of breath, anosmia, dysgeusia and ageusia, headache, chest pain, and sneezing had strong correlations (r>0.60, P<.001) to both new daily confirmed cases and deaths from COVID-19. GT COVID-19 (search term) and GT coronavirus (virus) searches predated real-world confirmed cases by 12 days (r=0.85, SD 0.10 and r=0.76, SD 0.09, respectively, P<.001). Searches for symptoms of diarrhea, fever, shortness of breath, cough, nasal obstruction, and rhinorrhea all had a negative lag greater than 1 week compared to new daily cases, while searches for anosmia and dysgeusia peaked worldwide and in China with positive lags of 5 days and 6 weeks, respectively, corresponding with widespread media coverage of these symptoms in COVID-19. Conclusions: This study demonstrates the utility of digital epidemiology in providing helpful surveillance data of disease outbreaks like COVID-19. Although certain online search trends for this disease were influenced by media coverage, many search terms reflected clinical manifestations of the disease and showed strong correlations with real-world cases and deaths