Solar Irradiance Variability and Climate

The brightness of the Sun varies on all time scales on which it has been observed, and there is increasing evidence that it has an influence on climate. The amplitudes of such variations depend on the wavelength and possibly on the time scale. Although many aspects of this variability are well established, the exact magnitude of secular variations (going beyond a solar cycle) and the spectral dependence of variations are under discussion. The main drivers of solar variability are thought to be magnetic features at the solar surface. The climate reponse can be, on a global scale, largely accounted for by simple energetic considerations, but understanding the regional climate effects is more difficult. Promising mechanisms for such a driving have been identified, including through the influence of UV irradiance on the stratosphere and dynamical coupling to the surface. Here we provide an overview of the current state of our knowledge, as well as of the main open questions

Evidence for polar jets as precursors of polar plume formation

Observations from the Hinode/XRT telescope and STEREO/SECCHI/EUVI are utilized to study polar coronal jets and plumes. The study focuses on the temporal evolution of both structures and their relationship. The data sample, spanning April 7-8 2007, shows that over 90% of the 28 observed jet events are associated with polar plumes. EUV images (STEREO/SECCHI) show plume haze rising from the location of approximately 70% of the polar X-ray (Hinode/XRT) and EUV jets, with the plume haze appearing minutes to hours after the jet was observed. The remaining jets occurred in areas where plume material previously existed causing a brightness enhancement of the latter after the jet event. Short-lived, jet-like events and small transient bright points are seen (one at a time) at different locations within the base of pre-existing long-lived plumes. X-ray images also show instances (at least two events) of collimated-thin jets rapidly evolving into significantly wider plume-like structures that are followed by the delayed appearance of plume haze in the EUV. These observations provide evidence that X-ray jets are precursors of polar plumes, and in some cases cause brightenings of plumes. Possible mechanisms to explain the observed jet and plume relationship are discussed.Comment: 10 pages, 4 figures, accepted as APJ Lette

Magneto-mechanical interplay in spin-polarized point contacts

We investigate the interplay between magnetic and structural dynamics in ferromagnetic atomic point contacts. In particular, we look at the effect of the atomic relaxation on the energy barrier for magnetic domain wall migration and, reversely, at the effect of the magnetic state on the mechanical forces and structural relaxation. We observe changes of the barrier height due to the atomic relaxation up to 200%, suggesting a very strong coupling between the structural and the magnetic degrees of freedom. The reverse interplay is weak, i.e. the magnetic state has little effect on the structural relaxation at equilibrium or under non-equilibrium, current-carrying conditions.Comment: 5 pages, 4 figure

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

The Influence of Magnetic Field on Oscillations in the Solar Chromosphere

Two sequences of solar images obtained by the Transition Region and Coronal Explorer in three UV passbands are studied using wavelet and Fourier analysis and compared to the photospheric magnetic flux measured by the Michelson Doppler Interferometer on the Solar Heliospheric Observatory to study wave behaviour in differing magnetic environments. Wavelet periods show deviations from the theoretical cutoff value and are interpreted in terms of inclined fields. The variation of wave speeds indicates that a transition from dominant fast-magnetoacoustic waves to slow modes is observed when moving from network into plage and umbrae. This implies preferential transmission of slow modes into the upper atmosphere, where they may lead to heating or be detected in coronal loops and plumes.Comment: 8 pages, 6 figures (4 colour online only), accepted for publication in The Astrophysical Journa

A comparative study of the effect of dexmedetomidine and lignocaine on hemodynamic responses and recovery following tracheal extubation in patients undergoing intracranial surgery

Background: Recovery from general anesthesia and extubation is a period of intense physiological stress for patients. The most feared complications after intracranial surgery are development of an intracranial hematoma and major cerebral edema. Both may result in cerebral hypoperfusion and brain injury. Thus, the anesthetic emergence of a neurosurgical patient should include maintenance of stable respiratory and cardiovascular parameters. Minimal reaction to the endotracheal tube removal prevents sympathetic stimulation and increases in venous pressure. In our study, we compared dexmedetomidine HCl, lignocaine HCl and placebo to blunt stress response and providing a smooth transition from extubation phase.Methods: 75 ASA Grade I and II patients aged 18-60 years scheduled for elective intracranial surgery for intracranial space occupying lesions were randomly divided into three groups of 25 each. Balanced general anesthesia was given. Inhalation anesthetic was discontinued and after return of spontaneous respiration patient in Group D received injection dexmedetomidine 0.5 µg/kg intravenous (IV), Group X received injection lignocaine 1.5 mg/kg IV and Group P received 10 ml normal saline IV over 60 sec. Heart rate (HR), mean arterial pressure (MAP), quality of extubation were measured at 1, 3, 5, 10, 15 mins interval after extubation. Emergence time and extubation time were noted and quality of extubation was evaluated on cough grading.Results: There was a significant decrease in MAPs and HR in Group D as compared to Group L and Group P (p<0.05) at all-time interval after extubation. Extubation quality score of the majority of patients was 1 in Group D, 2 in Group X, and 3 in Group P (p<0.001). The duration of emergence and extubation were comparable in all three groups. Sedation score of the most patient was 3 (44%) in Group D and 2 (56%) in Group X. Six patients in Group D and 1 patient in Group X had bradycardia.Conclusion: Single bolus dose of IV dexmedetomidine HCl 0.5 mg/kg given before tracheal extubation effectively attenuates hemodynamic response to extubation as compared to 1.5 mg/kg lignocaine HCl

Improving multidisciplinary team working to support integrated care for people with frailty amidst the COVID-19 pandemic

Multidisciplinary team (MDT) working is essential to optimise and integrate services for people who are frail. MDTs require collaboration. Many health and social care professionals have not received formal training in collaborative working. This study investigated MDT training designed to help participants deliver integrated care for frail individuals during the Covid-19 pandemic. Researchers utilised a semi-structured analytical framework to support observations of the training sessions and analyse the results of two surveys designed to assess the training process and its impact on participants knowledge and skills. 115 participants from 5 Primary Care Networks in London attended the training. Trainers utilised a video of a patient pathway, encouraged discussion of it, and demonstrated the use of evidence-based tools for patient needs assessment and care planning. Participants were encouraged to critique the patient pathway, reflect on their own experiences of planning and providing patient care. 38% of participants completed a pre-training survey, 47% a post-training survey. Significant improvement in knowledge and skills were reported including understanding roles in contributing to MDT working, confidence to speak in MDT meetings, using a range of evidence-based clinical tools for comprehensive assessment and care planning. Greater levels of autonomy, resilience, and support for MDT working were reported. Training proved effective; it could be scaled up and adopted to other settings

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