Estimation of width and inclination of a filament sheet using He II 304 A observations by STEREO/EUVI

The STEREO mission has been providing stereoscopic view of the filament eruptions in EUV wavelengths. The most extended view during filament eruptions is seen in He II 304 \AA observations, as the filament spine appears darker and sharper. The projected filament width appears differently when viewed from different angles by STEREO satellites. Here, we present a method for estimating the width and inclination of the filament sheet using He II 304 \AA\ observations by STEREO-A and B satellites from the two viewpoints. The width of the filament sheet, when measured from its feet to its apex, gives estimate of filament height above the chromosphere.Comment: 9 pages, 2 figures, in Annales Geophysica

Impaired endothelial function of the retinal vasculature in hypertensive patients

<p><b>Background and Purpose:</b> Arterial hypertension constitutes a central factor in the pathogenesis of stroke. We examined endothelial function of the retinal vasculature as a model of the cerebral circulation.</p> <p><b>Methods:</b> Thirty-eight young subjects (19 hypertensive and 19 normotensive) were treated with the AT1-receptor blocker candesartan cilexetil and placebo, each over 7 days. Retinal capillary flow and blood flow velocity in the central retinal artery were assessed with scanning laser Doppler flowmetry and pulsed Doppler ultrasound, respectively. NG-monomethyl-L-arginine (L-NMMA) was infused to inhibit nitric oxide (NO) synthesis. Diffuse luminance flicker was applied to stimulate NO release.</p> <p><b>Results:</b> In normotensive subjects, L-NMMA decreased retinal capillary flow by 8.2%±13% (P<0.05) and flickering light increased mean blood flow velocity in the central retinal artery by 19%±29% (P<0.01). In contrast, no significant change to these provocative tests was seen in hypertensive subjects. Treatment with candesartan cilexetil restored a normal pattern of reactivity in retinal capillaries (L-NMMA: decrease in perfusion by 10%±17%, P<0.05) and the central retinal artery (flicker: increase in mean blood flow velocity by 42%±31%, P<0.001) in hypertensive patients.</p> <p><b>Conclusions:</b> Endothelial function of the retinal vasculature is impaired in early essential hypertension but can be improved by AT1-receptor blockade.</p&gt

Observations of Multiple Surges Associated with Magnetic Activities in AR10484 on 25 October 2003

We present a multiwavelength study of recurrent surges observed in H{\alpha}, UV (SOHO/EIT) and Radio (Learmonth, Australia) from the super-active region NOAA 10484 on 25 October, 2003. Several bright structures visible in H{\alpha} and UV corresponding to subflares are also observed at the base of each surge. Type III bursts are triggered and RHESSI X-ray sources are evident with surge activity. The major surge consists of the bunches of ejective paths forming a fan-shape region with an angular size of (\approx 65\degree) during its maximum phase. The ejection speed reaches upto \sim200 km/s. The SOHO/MDI magnetograms reveal that a large dipole emerges east side of the active region on 18-20 October 2003, a few days before the surges. On October 25, 2003, the major sunspots were surrounded by "moat regions" with moving magnetic features (MMFs). Parasitic fragmented positive polarities were pushed by the ambient dispersion motion of the MMFs and annihilated with negative polarities at the borders of the moat region of the following spot to produce flares and surges. A topology analysis of the global Sun using PFSS shows that the fan structures visible in the EIT 171 A images follow magnetic field lines connecting the present AR to a preceding AR in the South East. Radio observations of type III bursts indicate that they are coincident with the surges, suggesting that magnetic reconnection is the driver mechanism. The magnetic energy released by reconnection is transformed into plasma heating and provides the kinetic energy for the ejections. A lack of a radio signature in the high corona suggests that the surges are confined to follow the closed field lines in the fans. We conclude that these cool surges may have some local heating effects in the closed loops, but probably play a minor role in global coronal heating and the surge material does not escape to the solar wind.Comment: Accepted for the Publication in ApJ; 25 pages, 10 Figures, and 1 Tabl

Automated universal chip platform for fluorescence based cellular assays

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The advantage of cell based assays used as biosensors is the direct access to hardly obtainable parameters like toxicity, mutagenicity and pharmacological effectiveness. Within the last few years we established a micro fluidic platform including a peristaltic micro pump as well as several valves, manifolds and micro channels [1]. For optical online monitoring the micro fluidic system is bonded to a glass slide. Furthermore the biochip is fixed on an electrically heated support. The pneumatically actuated peristaltic pump as well as the temperature control is performed by a control device. For the fluorescence based online monitoring a robotic guided fluorescence measurement module was developed, which supports the detection of fluorescence in microtiter plates and microfluidic systems. This measurement module allows the fluorescence detection of two different excitation / detection wavelengths (480 / 530 nm and 570 / 620 nm) and was successfully characterised using EGFP and Rhodamine 6G. Additionally three cell based assays with bacterial, yeast and human cells were characterized

Recurrent Coronal Jets Induced by Repetitively Accumulated Electric Currents

Three extreme-ultraviolet (EUV) jets recurred in about one hour on 2010 September 17 in the following magnetic polarity of active region 11106. The EUV jets were observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board SDO measured the vector magnetic field, from which we derive the magnetic flux evolution, the photospheric velocity field, and the vertical electric current evolution. The magnetic configuration before the jets is derived by the nonlinear force-free field (NLFFF) extrapolation. We derive that the jets are above a pair of parasitic magnetic bipoles which are continuously driven by photospheric diverging flows. The interaction drove the build up of electric currents that we indeed observed as elongated patterns at the photospheric level. For the first time, the high temporal cadence of HMI allows to follow the evolution of such small currents. In the jet region, we found that the integrated absolute current peaks repetitively in phase with the 171 A flux evolution. The current build up and its decay are both fast, about 10 minutes each, and the current maximum precedes the 171 A by also about 10 minutes. Then, HMI temporal cadence is marginally fast enough to detect such changes. The photospheric current pattern of the jets is found associated to the quasi-separatrix layers deduced from the magnetic extrapolation. From previous theoretical results, the observed diverging flows are expected to build continuously such currents. We conclude that magnetic reconnection occurs periodically, in the current layer created between the emerging bipoles and the large scale active region field. It induced the observed recurrent coronal jets and the decrease of the vertical electric current magnitude.Comment: 10 pages, 7 figures, accepted for publication in A&

Interaction between a fast rotating sunspot and ephemeral regions as the origin of the major solar event on 2006 December 13

The major solar event on 2006 December 13 is characterized by the approximately simultaneous occurrence of a heap of hot ejecta, a great two-ribbon flare and an extended Earth-directed coronal mass ejection. We examine the magnetic field and sunspot evolution in active region NOAA AR 10930, the source region of the event, while it transited the solar disk centre from Dec. 10 to Dec. 13. We find that the obvious changes in the active region associated with the event are the development of magnetic shear, the appearance of ephemeral regions and fast rotation of a smaller sunspot. Around the area of the magnetic neutral line of the active region, interaction between the fast rotating sunspot and the ephemeral regions triggers continual brightening and finally the major flare. It is indicative that only after the sunspot rotates up to 200$^{\circ}$ does the major event take place. The sunspot rotates at least 240$^{\circ}$ about its centre, the largest sunspot rotation angle which has been reported.Comment: 4 pages, 6 figures, ApJ Letters inpres

3D evolution of a filament disappearance event observed by STEREO

A filament disappearance event was observed on 22 May 2008 during our recent campaign JOP 178. The filament, situated in the southern hemisphere, showed sinistral chirality consistent with the hemispheric rule. The event was well observed by several observatories in particular by THEMIS. One day before the disappearance, H$\alpha$ observations showed up and down flows in adjacent locations along the filament, which suggest plasma motions along twisted flux rope. THEMIS and GONG observations show shearing photospheric motions leading to magnetic flux canceling around barbs. STEREO A, B spacecraft with separation angle 52.4 degrees, showed quite different views of this untwisting flux rope in He II 304 \AA\ images. Here, we reconstruct the 3D geometry of the filament during its eruption phase using STEREO EUV He II 304 \AA\ images and find that the filament was highly inclined to the solar normal. The He II 304 \AA\ movies show individual threads, which oscillate and rise to an altitude of about 120 Mm with apparent velocities of about 100 km s$^{-1}$, during the rapid evolution phase. Finally, as the flux rope expands into the corona, the filament disappears by becoming optically thin to undetectable levels. No CME was detected by STEREO, only a faint CME was recorded by LASCO at the beginning of the disappearance phase at 02:00 UT, which could be due to partial filament eruption. Further, STEREO Fe XII 195 \AA\ images showed bright loops beneath the filament prior to the disappearance phase, suggesting magnetic reconnection below the flux rope

On the nature of prominence emission observed by SDO/AIA

The Prominence-Corona Transition Region (PCTR) plays a key role in the thermal and pressure equilibrium of solar prominences. Our knowledge of this interface is limited and several major issues remain open, including the thermal structure and, in particular, the maximum temperature of the detectable plasma. The high signal-to-noise ratio of images obtained by the Atmospheric Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory clearly show that prominences are often seen in emission in the 171 and 131 bands. We investigate the temperature sensitivity of these AIA bands for prominence observation, in order to infer the temperature content in an effort to explain the emission. Using the CHIANTI atomic database and previously determined prominence differential emission measure distributions, we build synthetic spectra to establish the main emission-line contributors in the AIA bands. We find that the Fe IX line always dominates the 171 band, even in the absence of plasma at > 10^6 K temperatures, while the 131 band is dominated by Fe VIII. We conclude that the PCTR has sufficient plasma emitting at > 4 10^5 K to be detected by AIA.Comment: accepted Ap

Solar prominence diagnostic with hinode/EIS

No abstract available