Radiated Immunity Testing of a Device with an External Wire: Repeatibility of Reverberation Chamber Results and Correlation with Anechoic Chamber Results

We present the experimental radiated immunity results of an electronic device with an external wire obtained in reverberation and anechoic chambers. Repeatability and reproducibility of reverberation chamber measurements are investigated by repeating the test in three reverberation chambers with different characteristics. We show how the current state of the art allows a statistical control of RC measurement repeatability within an industrial installation, and that a statistical correlation with AC results frequency by frequency is possible in particular cases relevant to automotive application

Plasma composition in a sigmoidal anemone active region

Using spectra obtained by the EIS instrument onboard Hinode, we present a detailed spatially resolved abundance map of an active region (AR)-coronal hole (CH) complex that covers an area of 359 arcsec x 485 arcsec. The abundance map provides first ionization potential (FIP) bias levels in various coronal structures within the large EIS field of view. Overall, FIP bias in the small, relatively young AR is 2-3. This modest FIP bias is a consequence of the AR age, its weak heating, and its partial reconnection with the surrounding CH. Plasma with a coronal composition is concentrated at AR loop footpoints, close to where fractionation is believed to take place in the chromosphere. In the AR, we found a moderate positive correlation of FIP bias with nonthermal velocity and magnetic flux density, both of which are also strongest at the AR loop footpoints. Pathways of slightly enhanced FIP bias are traced along some of the loops connecting opposite polarities within the AR. We interpret the traces of enhanced FIP bias along these loops to be the beginning of fractionated plasma mixing in the loops. Low FIP bias in a sigmoidal channel above the AR's main polarity inversion line where ongoing flux cancellation is taking place, provides new evidence of a bald patch magnetic topology of a sigmoid/flux rope configfiuration.Comment: For on-line animation, see http://www.mssl.ucl.ac.uk/~db2/fip_intensity.gif. Accepted by Ap

Interplanetary Magnetic Field Guiding Relativistic Particles

The origin and the propagation of relativistic solar particles (0.5 to few Ge V) in the interplanetary medium remains a debated topic. These relativistic particles, detected at the Earth by neutron monitors have been previously accelerated close to the Sun and are guided by the interplanetary magnetic field (IMF) lines, connecting the acceleration site and the Earth. Usually, the nominal Parker spiral is considered for ensuring the magnetic connection to the Earth. However, in most GLEs the IMF is highly disturbed, and the active regions associated to the GLEs are not always located close to the solar footprint of the nominal Parker spiral. A possible explanation is that relativistic particles are propagating in transient magnetic structures, such as Interplanetary Coronal Mass Ejections (ICMEs). In order to check this interpretation, we studied in detail the interplanetary medium where the particles propagate for 10 GLEs of the last solar cycle. Using the magnetic field and the plasma parameter measurements (ACE/MAG and ACE/SWEPAM), we found widely different IMF configurations. In an independent approach we develop and apply an improved method of the velocity dispersion analysis to energetic protons measured by SoHO/ERNE. We determined the effective path length and the solar release time of protons from these data and also combined them with the neutron monitor data. We found that in most of the GLEs, protons propagate in transient magnetic structures. Moreover, the comparison between the interplanetary magnetic structure and the interplanetary length suggest that the timing of particle arrival at Earth is dominantly determined by the type of IMF in which high energetic particles are propagating. Finally we find that these energetic protons are not significantly scattered during their transport to Earth

The 3D structure of an active region filament as extrapolated from photospheric and chromospheric observations

The 3D structure of an active region (AR) filament is studied using nonlinear force-free field (NLFFF) extrapolations based on simultaneous observations at a photospheric and a chromospheric height. To that end, we used the Si I 10827 \AA\ line and the He I 10830 \AA\ triplet obtained with the Tenerife Infrared Polarimeter (TIP) at the VTT (Tenerife). The two extrapolations have been carried out independently from each other and their respective spatial domains overlap in a considerable height range. This opens up new possibilities for diagnostics in addition to the usual ones obtained through a single extrapolation from, typically, a photospheric layer. Among those possibilities, this method allows the determination of an average formation height of the He I 10830 \AA\ signal of \approx 2 Mm above the surface of the sun. It allows, as well, to cross-check the obtained 3D magnetic structures in view of verifying a possible deviation from the force- free condition especially at the photosphere. The extrapolations yield a filament formed by a twisted flux rope whose axis is located at about 1.4 Mm above the solar surface. The twisted field lines make slightly more than one turn along the filament within our box, which results in 0.055 turns/Mm. The convex part of the field lines (as seen from the solar surface) constitute dips where the plasma can naturally be supported. The obtained 3D magnetic structure of the filament depends on the choice of the observed horizontal magnetic field as determined from the 180\circ solution of the azimuth. We derive a method to check for the correctness of the selected 180\circ ambiguity solution.Comment: 31 pages, 13 figures, ApJ Accepte

Coronal magnetic reconnection driven by CME expansion -- the 2011 June 7 event

Coronal mass ejections (CMEs) erupt and expand in a magnetically structured solar corona. Various indirect observational pieces of evidence have shown that the magnetic field of CMEs reconnects with surrounding magnetic fields, forming, e.g., dimming regions distant from the CME source regions. Analyzing Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on 2011 June 7, we present the first direct evidence of coronal magnetic reconnection between the fields of two adjacent ARs during a CME. The observations are presented jointly with a data-constrained numerical simulation, demonstrating the formation/intensification of current sheets along a hyperbolic flux tube (HFT) at the interface between the CME and the neighbouring AR 11227. Reconnection resulted in the formation of new magnetic connections between the erupting magnetic structure from AR 11226 and the neighboring active region AR 11227 about 200 Mm from the eruption site. The onset of reconnection first becomes apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, is re-directed towards remote areas in AR 11227, tracing the change of large-scale magnetic connectivity. The location of the coronal reconnection region becomes bright and directly observable at SDO/AIA wavelengths, owing to the presence of down-flowing cool, dense (10^{10} cm^{-3}) filament plasma in its vicinity. The high-density plasma around the reconnection region is heated to coronal temperatures, presumably by slow-mode shocks and Coulomb collisions. These results provide the first direct observational evidence that CMEs reconnect with surrounding magnetic structures, leading to a large-scale re-configuration of the coronal magnetic field.Comment: 12 pages, 12 figure

Vectorial Ribaucour Transformations for the Lame Equations

The vectorial extension of the Ribaucour transformation for the Lame equations of orthogonal conjugates nets in multidimensions is given. We show that the composition of two vectorial Ribaucour transformations with appropriate transformation data is again a vectorial Ribaucour transformation, from which it follows the permutability of the vectorial Ribaucour transformations. Finally, as an example we apply the vectorial Ribaucour transformation to the Cartesian background.Comment: 12 pages. LaTeX2e with AMSLaTeX package

Estimating equivalent bottom geoacoustial parameters from broadband inversion

A simple and fast approach to retrieve equivalent geoacoustic parameters is presented in this paper. The method is based upon the processing of 300-800 Hz broadband signals on a single hydrophone.Two stable characteristics of the impulse response of the shallow water waveguide are estimated: the time dispersion and the bottom reflection amplitudes. This two features are analytically linked to the compressional speed and to the attenuation coefficient of the medium. The inversion of the two latter geoacoustic parameters is straightforward since it relies on an analytical expression. The method is tested on INTIMATE96 data. The results show an excellent agreement between the reflection of the true medium and the reflection coefficient of the equivalent medium.The partners of the INTIMATE project wish to thank the staff of NRP ANDROMEDA, the staff of BO D’ENTRECASTEAUX and people of Mission Océanographique de l’Atlantique (aboard D’ENTRECASTEAUX). We also wish to thank the SACLANT Undersea Research Center for lending the Portable Array System and Roberto Chiarabini (SACLANTCEN) for his participation in the array preparation, deployment and use. Thanks to T. Folegot and G. Bonnaillie (CMO) for their active contribution in this work. The study was jointly sponsored by SHOM (exploratory program 95901), the Portuguese Ministery of Research (PRAXIS XXI) and ONR (contract N00014-95-1-0558)

Pulsed Flows Along a Cusp Structure Observed with SOO/AIA

We present observations of a cusp-shaped structure that formed after a flare and coronal mass ejection on 14 February 2011. Throughout the evolution of the cusp structure, blob features up to a few Mm in size were observed flowing along the legs and stalk of the cusp at projected speeds ranging from 50 to 150 km/sec. Around two dozen blob features, on order of 1 - 3 minutes apart, were tracked in multiple AlA EUV wavelengths. The blobs flowed outward (away from the Sun) along the cusp stalk, and most of the observed speeds were either constant or decelerating. We attempt to reconstruct the 3-D magnetic field of the evolving structure, discuss the possible drivers of the flows (including pulsed reconnect ion and tearing mode instability), and compare the observations to studies of pulsed reconnect ion and blob flows in the solar wind and the Earth's magnetosphere