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Lim T.-H.,Korea Advanced Institute of Science and Technology | Min K.-W.,Korea Advanced Institute of Science and Technology | Seon K.-I.,Korea Astronomy and Space Science Institute KASI
Astrophysical Journal

We have constructed a far-ultraviolet (FUV) continuum map of the Taurus-Auriga-Perseus complex, one of the largest local associations of dark clouds, by merging the two data sets of Galaxy Evolution Explorer and FUV Imaging Spectrograph, which made observations at similar wavelengths. The FUV intensity varies significantly across the whole region, but the diffuse FUV continuum is dominated by dust scattering of stellar photons. A diffuse FUV background of 1000 CU is observed, part of which may be attributable to the scattered photons of foreground FUV light, located in front of the thick clouds. The fluorescent emission of molecular hydrogen constitutes 10% of the total FUV intensity throughout the region, generally proportional to the local continuum level. We have developed a Monte Carlo radiative transfer code and applied it to the present clouds complex to obtain the optical properties of dust grains and the geometrical structures of the clouds. The albedo and the phase function asymmetry factor were estimated to be 0.42+0.05-0.05, and 0.47 +0.11-0.27, respectively, in accordance with theoretical estimations as well as recent observations. The distance and thickness of the four prominent clouds in this complex were estimated using a single-slab model applied individually to each cloud. The results obtained were in good agreement with those from other observations of the Taurus cloud, as its geometrical structure is rather simple. For other clouds that were observed to have multiple components, the results gave distances and thicknesses encompassing all of the components of each cloud. The distance and thickness estimations were not crucially sensitive to the exact values of the albedo and the phase function asymmetry factor, while the locations of the bright field stars relative to the clouds as initial photon sources seem to be the most important factor in the process of fitting. © 2013. The American Astronomical Society. All rights reserved. Source

Kumar P.,Korea Astronomy and Space Science Institute KASI | Manoharan P.K.,Tata Institute of Fundamental Research
Astronomy and Astrophysics

We present a multiwavelength study of the formation and ejection of a plasma blob and associated extreme ultraviolet (EUV) waves in active region (AR) NOAA 11176, observed by SDO/AIA and STEREO on 25 March 2011. The EUV images observed with the AIA instrument clearly show the formation and ejection of a plasma blob from the lower atmosphere of the Sun at ~9 min prior to the onset of the M1.0 flare. This onset of the M-class flare happened at the site of the blob formation, while the blob was rising in a parabolic path with an average speed of ~300 km s. The blob also showed twisting and de-twisting motion in the lower corona, and the blob speed varied from ~10-540 km s. The faster and slower EUV wavefronts were observed in front of the plasma blob during its impulsive acceleration phase. The faster EUV wave propagated with a speed of ~785 to 1020 km s, whereas the slower wavefront speed varied in between ~245 and 465 km s. The timing and speed of the faster wave match the shock speed estimated from the drift rate of the associated type II radio burst. The faster wave experiences a reflection by the nearby AR NOAA 11177. In addition, secondary waves were observed (only in the 171 Å channel), when the primary fast wave and plasma blob impacted the funnel-shaped coronal loops. The Helioseismic Magnetic Imager (HMI) magnetograms revealed the continuous emergence of new magnetic flux along with shear flows at the site of the blob formation. It is inferred that the emergence of twisted magnetic fields in the form of arch-filaments/ "anemone-type" loops is the likely cause for the plasma blob formation and associated eruption along with the triggering of M-class flare. Furthermore, the faster EUV wave formed ahead of the blob shows the signature of fast-mode MHD wave, whereas the slower wave seems to be generated by the field line compression by the plasma blob. The secondary wave trains originated from the funnel-shaped loops are probably the fast magnetoacoustic waves. © ESO 2013. Source

Kumar P.,Korea Astronomy and Space Science Institute KASI | Kumar P.,Max Planck Institute for Solar System Research | Innes D.E.,Max Planck Institute for Solar System Research
Solar Physics

Images of an east-limb flare on 3 November 2010 taken in the 131 Å channel of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory provide a convincing example of a long current sheet below an erupting plasmoid, as predicted by the standard magnetic reconnection model of eruptive flares. However, the 171 Å and 193 Å channel images hint at an alternative scenario. These images reveal that large-scale waves with velocity greater than 1000 km s-1 propagated alongside and ahead of the erupting plasmoid. Just south of the plasmoid, the waves coincided with type-II radio emission, and to the north, where the waves propagated along plume-like structures, there was increased decimetric emission. Initially, the cavity around the hot plasmoid expanded. Later, when the erupting plasmoid reached the height of an overlying arcade system, the plasmoid structure changed, and the lower parts of the cavity collapsed inwards. Hot loops appeared alongside and below the erupting plasmoid. We consider a scenario in which the fast waves and the type-II emission were a consequence of a flare blast wave, and the cavity collapse and the hot loops resulted from the break-out of the flux rope through an overlying coronal arcade. © 2013 Springer Science+Business Media Dordrecht. Source

Kumar P.,Korea Astronomy and Space Science Institute KASI | Kumar P.,Max Planck Institute for Solar System Research | Innes D.E.,Max Planck Institute for Solar System Research | Inhester B.,Max Planck Institute for Solar System Research
Astrophysical Journal Letters

We report high resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) of intensity oscillations in a hot, T ∼ 8-10 MK, loop. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop's footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94 Å channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94 Å channels. The characteristic period and the decay time of the oscillation were ∼630 and ∼440 s, respectively. The phase speed was about 460-510 km s-1 which roughly matches the sound speed of the loop (430-480 km s-1). The observed properties of the oscillation are consistent with the observations of Dopper-shift oscillations discovered by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. The wave bounces back and forth a couple of times before fading. © 2013. The American Astronomical Society. All rights reserved. Source

Farzinnia A.,Korea Basic Science Institute | Kouwn S.,Korea Astronomy and Space Science Institute KASI
Physical Review D - Particles, Fields, Gravitation and Cosmology

We introduce a minimal and yet comprehensive framework with CP and classical scale symmetries in order to simultaneously address the hierarchy problem, neutrino masses, dark matter, and inflation. One complex gauge singlet scalar and three flavors of the right-handed Majorana neutrinos are added to the standard model content, facilitating the see-saw mechanism, among others. An adimensional theory of gravity (Agravity) is employed, allowing for the trans-Planckian field excursions. The weak and Planck scales are induced by the Higgs portal and the scalar nonminimal couplings, respectively, once a Coleman-Weinberg dynamically generated vacuum expectation value for the singlet scalar is obtained. All scales are free from any mutual quadratic destabilization. The CP symmetry prevents a decay of the pseudoscalar singlet, rendering it a suitable WIMPzilla dark matter candidate with the correct observational relic abundance. Identifying the pseudo-Nambu-Goldstone boson of the (approximate) scale symmetry with the inflaton field, the model accommodates successful slow-roll inflation, compatible with the observational data. We reach the conclusion that a pseudo-Nambu-Goldstone inflaton, within a classically scale-symmetric framework, yields lighter WIMPzillas. © 2016 American Physical Society. Source

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