Hα Doppler shifts in a tornado in the solar corona

Context. High resolution movies in 193 Å from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO) show apparent rotation in the leg of a prominence observed during a coordinated campaign. Such structures are commonly referred to as tornadoes. Time-distance intensity diagrams of the AIA data show the existence of oscillations suggesting that the structure is rotating. Aims. The aim of this paper is to understand if the cool plasma at chromospheric temperatures inside the tornado is rotating around its central axis. Methods. The tornado was also observed in Hα with a cadence of 30 s by the MSDP spectrograph, operating at the Solar Tower in Meudon. The MSDP provides sequences of simultaneous spectra in a 2D field of view from which a cube of Doppler velocity maps is retrieved. Results. The Hα Doppler maps show a pattern with alternatively blueshifted and redshifted areas of 5 to 10′′ wide. Over time the blueshifted areas become redshifted and vice versa, with a quasi-periodicity of 40 to 60 min. Weaker amplitude oscillations with periods of 4 to 6 min are superimposed onto these large period oscillations. Conclusions. The Doppler pattern observed in Hα cannot be interpreted as rotation of the cool plasma inside the tornado. The Hα velocity observations give strong constraints on the possible interpretations of the AIA tornado

Open questions on prominences from coordinated observations by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP

Context. A large prominence was observed on September 24, 2013, for three hours (12:12 UT -15:12 UT) with the newly launched (June 2013) Interface Region Imaging Spectrograph (IRIS), THEMIS (Tenerife), the Hinode Solar Optical Telescope (SOT), the Solar Dynamic Observatory Atmospheric Imaging Assembly (SDO/AIA), and the Multichannel Subtractive Double Pass spectrograph (MSDP) in the Meudon Solar Tower. Aims. The aim of this work is to study the dynamics of the prominence fine structures in multiple wavelengths to understand their formation. Methods. The spectrographs IRIS and MSDP provided line profiles with a high cadence in Mg II and in Halpha lines. Results. The magnetic field is found to be globally horizontal with a relatively weak field strength (8-15 Gauss). The Ca II movie reveals turbulent-like motion that is not organized in specific parts of the prominence. On the other hand, the Mg II line profiles show multiple peaks well separated in wavelength. Each peak corresponds to a Gaussian profile, and not to a reversed profile as was expected by the present non-LTE radiative transfer modeling. Conclusions. Turbulent fields on top of the macroscopic horizontal component of the magnetic field supporting the prominence give rise to the complex dynamics of the plasma. The plasma with the high velocities (70 km/s to 100 km/s if we take into account the transverse velocities) may correspond to condensation of plasma along more or less horizontal threads of the arch-shape structure visible in 304 A. The steady flows (5 km/s) would correspond to a more quiescent plasma (cool and prominence-corona transition region) of the prominence packed into dips in horizontal magnetic field lines. The very weak secondary peaks in the Mg II profiles may reflect the turbulent nature of parts of the prominence.Comment: 15 pages, 14 figure

Chemical and rheological aspects of gel formation in the California Mastitis Test

The rheological properties of the CMT gel were analysed. Data are presented to demonstrate that the gel is a non-homogenous, visco-elastic, non-Newtonian fluid with rheopectic, and rheodestructive behaviour. The fundamental chemistry of the CMT is reviewed and a modified theory of gel formation is presented. The implications of the rheological properties and modified theory of gel formation for an automatic sensor are discussed

Uitbreiding bevoegdheden ter handhaving van de openbare orde en veiligheid

De bevoegdheden van de burgemeester ter handhaving van de openbare orde en veiligheid zijn de laatste tijd fors uitgebreid en er is nog een aantal bevoegdheden in voorbereiding. Deze bevoegdheden moeten de burgemeester in staat stellen snel op te treden tegen ordeverstoringen en onveiligheid. Bijzonder is dat de burgemeester zijn nieuwe bevoegdheden, onder omstandigheden en voorwaarden, preventief kan gebruiken en toepassen op groepen ordeverstoorders. Ook kan hij de bewegingsvrijheid en privacy van betrokkenen flink inperken. Dit betekent dat hij terughoudend en zorgvuldig met die bevoegdheden moet omgaan. Als hij zich te veel profileert als crimefighter, verspeelt hij het vertrouwen als burgervader

Voorzorg en bestuurlijke handhaving

Inleiding In deze bijdrage belicht ik enkele bestuurlijke bevoegdheden ter handhaving van de openbare orde en veiligheid vanuit het perspectief van de voorzorgcultuur, zoals door Pieterman beschreven (Pieterman, 2008). Deze bevoegdheden, waaronder bestuurlijke ophouding, preventief fouilleren, cameratoezicht en gebieds-, samenscholings- en huisverboden, beantwoorden aan een sterke roep om orde en veiligheid in het publieke domein. Ze passen in zekere zin in het voorzorgdenken. Toepassing van deze bevoegdheden is effectief in relatie tot onzekere bedreigingen van de openbare orde en veiligheid. We betalen er wel een hoge prijs voor

On mesogranulation, network formation and supergranulation

We present arguments which show that in all likelihood mesogranulation is not a true scale of solar convection but the combination of the effects of both highly energetic granules, which give birth to strong positive divergences (SPDs) among which we find exploders, and averaging effects of data processing. The important role played by SPDs in horizontal velocity fields appears in the spectra of these fields where the scale $\sim$4 Mm is most energetic; we illustrate the effect of averaging with a one-dimensional toy model which shows how two independent non-moving (but evolving) structures can be transformed into a single moving structure when time and space resolution are degraded. The role of SPDs in the formation of the photospheric network is shown by computing the advection of floating corks by the granular flow. The coincidence of the network bright points distribution and that of the corks is remarkable. We conclude with the possibility that supergranulation is not a proper scale of convection but the result of a large-scale instability of the granular flow, which manifests itself through a correlation of the flows generated by SPDs.Comment: 10 pages, 11 figures, to appear in Astronomy and Astrophysic

Velocity vectors of a quiescent prominence observed by Hinode/SOT and the MSDP (Meudon)

The dynamics of prominence fine structures is a challenge to understand the formation of cool plasma prominence embedded in the hot corona. Recent observations from the high resolution Hinode/SOT telescope allow us to compute velocities perpendicularly to the line-of-sight or transverse velocities. Combining simultaneous observations obtained in H-alpha with Hinode/SOT and the MSDP spectrograph operating in the Meudon solar tower we derive the velocity vectors of a quiescent prominence. The velocities perpendicular to the line-of-sight are measured by time slice technique, the Dopplershifts by the bisector method. The Dopplershifts of bright threads derived from the MSDP reach 15 km/s at the edges of the prominence and are between +/- 5 km/s in the center of the prominence. Even though they are minimum values due to seeing effect, they are of the same order as the transverse velocities. These measurements are very important because they suggest that the verticalstructures shown in SOT may not be real vertical magnetic structures in the sky plane. The vertical structures could be a pile up of dips in more or less horizontal magnetic field lines in a 3D perspective, as it was proposed by many MHD modelers. In our analysis we also calibrate the Hinode H-alpha data using MSDP observations obtained simultaneously.Comment: 7 pages, 7 figures, submitted to A &

Filament eruption connected to protospheric activity

Two cases of activation of filaments that occured in regions of intense magnetic activity was studied. The simultaneous observations from Debrecen Observatory (white light and H alpha filtergram), and from Meudon Observatory (magnetogram, MSDP dopplergram and intensity maps in H alpha) gave a complementary set of data from which can be produced evidence of the influence of the photospheric magnetic field on the destabilization process of the filaments. On June 22, 1980, the eruption of the filament is associated with the motion of pores, which are manifestations of emerging flux knots. On September 3, 1980, the twisting motions in the filament are associated to the birth of a pore in its neighborhood. These observations are discussed

Kroniek Openbare Orde 2010

Inleiding: In deze kroniek beschrijf ik in vogelvlucht een aantal ontwikkelingen dat zich in 2010 heeft voorgedaan op het gebied van het openbare orderecht. Allereerst behandel ik nieuwe en op stapel staande wetgeving. In het verlengde daarvan sta ik stil bij de gestage uitbreiding van de portefeuille van de burgemeester. Vervolgens behandel ik enkele relevante rechterlijke uitspraken. Tot besluit attendeer ik op interessante publicaties en websites

New Pedetidae (Rodentia: Mammalia) from the Mio-Pliocene of Africa

International audiencePedetidae, or springhares, are represented by a single extant genus (Pedetes) and five extinct ones (Parapedetes, Megapedetes, Propedetes, Rusingapedetes and Oldrichpedetes of which the latter two are new). The fossil record of pedetids tends to be scanty, but remains have been found in Southern Africa, East Africa, the Maghreb, the Arabian Peninsula, Turkey and Greece. Most of the localities have yielded only a few isolated teeth. We here describe some of the abundant fossil material from Namibia and Kenya, which throws a great deal of light on the family