Evolution of helicity in NOAA 10923 over three consecutive solar rotations

We have studied the evolution of magnetic helicity and chirality in an active region over three consecutive solar rotations. The region when it first appeared was named NOAA10923 and in subsequent rotations it was numbered NOAA 10930, 10935 and 10941. We compare the chirality of these regions at photospheric, chromospheric and coronal heights. The observations used for photospheric and chromospheric heights are taken from Solar Vector Magnetograph (SVM) and H_alpha imaging telescope of Udaipur Solar Observatory (USO), respectively. We discuss the chirality of the sunspots and associated H_alpha filaments in these regions. We find that the twistedness of superpenumbral filaments is maintained in the photospheric transverse field vectors also. We also compare the chirality at photospheric and chromospheric heights with the chirality of the associated coronal loops, as observed from the HINODE X-Ray Telescope.Comment: 8 pages, 4 figure

On the flare induced seismicity in the active region NOAA 10930 and related enhancement of global waves in the sun

A major flare (of class X3.4) occurred on 13 December 2006 in the active region NOAA 10930. The energy released during flares is also known to induce acoustic oscillations in the Sun. Here, we analyze the line-of-sight velocity patterns in this active region during the X3.4 flare using the Dopplergrams obtained by GONG instrument. We have also analyzed the disk-integrated velocity observations of the Sun obtained by GOLF instrument onboard SOHO spacecraft as well as full-disk collapsed velocity signals from GONG observations during this flare to study any possible connection between the flare related changes seen in the local and global velocity oscillations in the Sun. We apply wavelet transform to the time series of the localized velocity oscillations as well as the global velocity oscillations in the Sun spanning the flare event. The line-of-sight velocity shows significant enhancement in some localized regions of the penumbra of this active region during the flare. The affected region is seen to be away from the locations of the flare ribbons and the hard X-ray footpoints. The sudden enhancement in this velocity seems to be caused by the Lorentz force driven by the "magnetic jerk" in the localized penumbral region. Application of wavelet analysis to these flare induced localized seismic signals show significant enhancement in the high-frequency domain (5-8 mHz) and a feeble enhancement in the p-mode oscillations (2-5 mHz) during the flare. On the other hand, the wavelet analysis of GOLF velocity data and the full-disk collapsed GONG velocity data spanning the flare event indicate significant post-flare enhancements in the high-frequency global velocity oscillations in the Sun. We find indications of a connection between flare induced localized seismic signals and the excitation of global high-frequency oscillations in the Sun.Comment: 29 pages, 7 figures, To appear in The Astrophysical Journa

Evolution of Currents of Opposite Signs in the Flare Productive Solar Active Region NOAA 10930

Analysis of a time series of high spatial resolution vector magnetograms of the active region NOAA 10930 available from SOT/SP on-board Hinode revealed that there is a mixture of upward and downward currents in the two foot-points of an emerging flux-rope. The flux emergence rate is almost the same in both the polarities. We observe that along with an increase in magnetic flux, the net current in each polarity increases initially for about three days after which it decreases. This net current is characterized by having exactly opposite signs in each polarities while its magnitude remains almost the same most of the time. The decrease of net current in both the polarities is due to the increase of current having a sign opposite to that of the net current. The dominant current, with same sign as the net current, is seen to increase first and then decreases during the major X-class flares. Evolution of non-dominant current appears to be a necessary condition for a flare initiation. The above observations can have a plausible explanation in terms of the superposition of two different force-free states resulting in non-zero Lorentz force in the corona. This Lorentz force then push the coronal plasma and might facilitate the magnetic reconnection required for flares. Also, the evolution of the net current is found to follow the evolution of magnetic shear at the polarity inversion line.Comment: 24 pages, 6 figures, Submitted to Astrophysical Journa

Inhibition of NAADP signalling on reperfusion protects the heart by preventing lethal calcium oscillations via two-pore channel 1 and opening of the mitochondrial permeability transition pore

Aims In the heart, a period of ischaemia followed by reperfusion evokes powerful cytosolic Ca2+ oscillations that can cause lethal cell injury. These signals represent attractive cardioprotective targets, but the underlying mechanisms of genesis are ill-defined. Here, we investigated the role of the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP), which is known in several cell types to induce Ca2+ oscillations that initiate from acidic stores such as lysosomes, likely via two-pore channels (TPCs, TPC1 and 2). Methods and results An NAADP antagonist called Ned-K was developed by rational design based on a previously existing scaffold. Ned-K suppressed Ca2+ oscillations and dramatically protected cardiomyocytes from cell death in vitro after ischaemia and reoxygenation, preventing opening of the mitochondrial permeability transition pore. Ned-K profoundly decreased infarct size in mice in vivo. Transgenic mice lacking the endo-lysosomal TPC1 were also protected from injury. Conclusion NAADP signalling plays a major role in reperfusion-induced cell death and represents a potent pathway for protection against reperfusion injury

Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode

The main objective of this paper is to build and compare vector magnetic maps obtained by two spectral polarimeters, i.e. THEMIS/MTR and Hinode SOT/SP, using two inversion codes (UNNOFIT and MELANIE) based on the Milne-Eddington solar atmosphere model. To this end, we used observations of a facular region within active region NOAA 10996 on 23 May 2008, and found consistent results concerning the field strength, azimuth and inclination distributions. Because SOT/SP is free from the seeing effect and has better spatial resolution, we were able to resolve small magnetic polarities with sizes of 1" to 2", and we could detect strong horizontal magnetic fields, which converge or diverge in negative or positive facular polarities. These findings support models which suggest the existence of small vertical flux tube bundles in faculae. A new method is proposed to get the relative formation heights of the multi-lines observed by MTR assuming the validity of a flux tube model for the faculae. We found that the Fe 1 6302.5 \AA line forms at a greater atmospheric height than the Fe 1 5250.2 \AA line.Comment: 20 pages, 9 figures, 3 tables, accepted for publication in Solar Physic