Flows and Waves in Braided Solar Coronal Magnetic Structures

We study the high frequency dynamics in the braided magnetic structure of an active region (AR 11520) moss as observed by High-Resolution Coronal Imager (Hi-C). We detect quasi periodic flows and waves in these structures. We search for high frequency dynamics while looking at power maps of the observed region. We find that shorter periodicites (30 - 60 s) are associated with small spatial scales which can be resolved by Hi-C only. We detect quasi periodic flows with wide range of velocities from 13 - 185 km/s associated with braided regions. This can be interpreted as plasma outflows from reconnection sites. We also find presence of short period and large amplitude transverse oscillations associated with braided magnetic region. Such oscillations could be triggered by reconnection or such oscillation may trigger reconnection.Comment: 6 pages, 5 figures, Accepted for publication in ApJ Letter

2016: a year of dramatic changes in South Asia

Harsh V Pant reflects on how developments in 2016 highlight that the Modi government is gradually altering the foundations of Indian foreign policy. He notes that India’s non-committal attitude to the 17th non-alignment summit, combative Pakistan policy, and efforts to woo the US and key neighbours all indicate the South Asian strategic milieu is in flux and old rules no longer apply

Phase-locking in Multi-Frequency Brillouin Oscillator via Four Wave Mixing

Stimulated Brillouin scattering (SBS) and Kerr-nonlinear four wave-mixing (FWM) are among the most important and widely studied nonlinear effects in optical fibres. At high powers SBS can be cascaded producing multiple Stokes waves spaced by the Brillouin frequency shift. Here, we investigate the complex nonlinear interaction of the cascade of Stokes waves, generated in a Fabry-Perot chalcogenide fibre resonator through the combined action of SBS and FWM. We demonstrate the existence of parameter regimes, in which pump and Stokes waves attain a phase-locked steady state. Real-time measurements of 40ps pulses with 8GHz repetition rate are presented, confirming short-and long-term stability. Numerical simulations qualitatively agree with experiments and show the significance of FWM in phase-locking of pump and Stokes waves. Our findings can be applied for the design of novel picosecond pulse sources with GHz repetition rate for optical communication systems

First Imaging Observation of Standing Slow Wave in Coronal Fan loops

We observe intensity oscillations along coronal fan loops associated with the active region AR 11428. The intensity oscillations were triggered by blast waves which were generated due to X-class flares in the distant active region AR 11429. To characterise the nature of oscillations, we created time-distance maps along the fan loops and noted that the intensity oscillations at two ends of the loops were out of phase. As we move along the fan loop, the amplitude of the oscillations first decreased and then increased. The out-of-phase nature together with the amplitude variation along the loop implies that these oscillations are very likely to be standing waves. The period of the oscillations are estimated to be $\sim$27 min, damping time to be $\sim$45 min and phase velocity projected in the plane of sky $\sim$ 65-83 km s$^{-1}$. The projected phase speeds were in the range of acoustic speed of coronal plasma at about 0.6 MK which further indicates that these are slow waves. To best of our knowledge, this is the first report on the existence of the standing slow waves in non-flaring fan loops.Comment: 12 pages, 4 figures. Accepted for publication in ApJ

The ion-aerosol interactions from the ion mobility and aerosol particle size distribution measurements on January 17 and February 18, 2005 at Maitri, Antarctica - A case study

A case study for the ion–aerosol interactions is presented from the simultaneous measurements of mobility spectra of atmospheric ions in the mobility range of 2.29 to 2.98 × 10 − 4 cm2 V − 1 s −1 (diameter range 0.41–109 nm) and of size distribution of atmospheric aerosol particles in the size ranges of 4.4–700 nm and 500–20,000 nm diameters made at Maitri (70°45′52′ ′S, 11°44′2.7′ ′E; 130 m above mean sea level), Antarctica, on two days January 17 and February 18, 2005, with contrasting meteorological conditions. In contrast to January 17, on February 18, winds were stronger from the morning to noon and lower from the noon to evening, atmospheric pressure was lower, cloudiness was more, the land surface remained snow-covered after a blizzard on February 16 and 17 and the airmass over Maitri, descended from an altitude of ~3 km after an excursion over ocean. On these days mobility spectra showed two modes, corresponding to intermediate ions and light large ions and an indication of additional one/two maxima for small/cluster ions and heavy large ions. The small ions generated by cosmic rays, and the nucleation mode particles generated probably by photochemical reactions grew in size by condensation of volatile trace gases on them and produced the cluster and intermediate ion modes and the Aitken particle mode in ion/particle spectra. Particles in the size range of 9–26 nm have been estimated to grow at the rate of 1.9 nm h − 1 on February 18, 2005. Both, ions and aerosol particles show bimodal size distributions in the 16–107 nm size range, and comparison of the two size distributions suggests the formation of multiple charged ions. Attachment of small ions to particles in this bimodal distribution of Aitken particles together with the formation of multiple charged ions are proposed to result in the light and heavy large ion modes. Growth of the nucleation mode particles on February 18, 2005 is associated with the passage of the airmass over ocean. In contrast, though the ion size distributions were not much different, the aerosol size distributions did not show a dominant peak for the formation and growth of nucleation mode particles on January 17. More measurements are needed before the conclusion of this case study is generalized

Changes in concentration and size distribution of aerosols during fog over the south Indian Ocean

Measurements of the concentration and size distribution of aerosol particles in the size-ranges of 0.5-20 μm and 16-700 nm diameters were made during six fog episodes over the south Indian Ocean. Observations show that concentrations of particles of all sizes start decreasing 1-2 hours before the occurrence of fog. This decrease is more prominent for coarse particles of >1 μm diameter and continues until 10-20 minutes before the onset of fog when particle concentrations in all size ranges rapidly increase by one/two orders of magnitude in ~20 minutes. Thereafter, concentrations of particles of all sizes gradually decrease until the dissipation of fog. After the fog dissipation, concentrations of coarse mode particles rapidly increase and restore to their pre-fog levels but concentrations of the Aitken mode particles decrease slowly and reach their pre-fog levels only after 1-2 hours. The net effect of fog is to change the bimodal size distributions of aerosols with a coarse mode at 1.0 μm and an accumulation mode at 40-60 nm to a power law size distribution. It is proposed that the preferential growth and sedimentation of the coarse mode hygroscopic particles in the initial phase cause a large decrease in the aerosol surface area. As a result, the low vapour pressure gases which were initially being used for the growth of coarse mode particles, now accelerate the growth rates of the accumulation and Aitken mode particles

Observational evidence for the plausible linkage of Equatorial Electrojet (EEJ) electric field variations with the post sunset F-region electrodynamics

The paper is based on a detailed observational study of the Equatorial Spread F (ESF) events on geomagnetically quiet (<I>A<sub>p</sub></I>≤20) days of the solar maximum (2001), moderate (2004) and minimum (2006) years using the ionograms and magnetograms from the magnetic equatorial location of Trivandrum (8.5° N; 77° E; dip lat ~0.5° N) in India. The study brings out some interesting aspects of the daytime Equatorial Electrojet (EEJ) related electric field variations and the post sunset F-region electrodynamics governing the nature of seasonal characteristics of the ESF phenomena during these years. The observed results seem to indicate a plausible linkage of daytime EEJ related electric field variations with pre-reversal enhancement which in turn is related to the occurrence of ESF. These electric field variations are shown to be better represented through a parameter, termed as "E", in the context of possible coupling between the E- and F-regions of the ionosphere. The observed similarities in the gross features of the variations in the parameter "E" and the F-region vertical drift (<I>V<sub>z</sub></I>) point towards the potential usage of the EEJ related parameter "E" as an useful index for the assessment of <I>V<sub>z</sub></I> prior to the occurrence of ESF

Tolerância ao calor de caprinos e ovinos sem-lã em Sobral.

Resumo: Caprinos das raças Canindé, Anglo-Nubiana e Bhuj e avinos sem-la Morada Nova e Santa Inês foram comparados quanta às temperaturas retais e taxa respiratoria, antes e imediatamente apos o exercício e durante o período de uma hora de repouso apos o0 exercicio, para avaliaçao da tolerância ao calor ambiental. Resultados mostraram que a temperatura retal inicial nao foi diferente entre as cinco raças; apos exercicio, elevou de 1,25ºC até 1,95ºC nas diferentes raças; nao houve diferença da elevaçao da temperatura corporal entre espécies. Apos exercício, a recuperaçao foi rapida nos caprinos Bhuj e Canindé. A recuperaçao foi mais lenta na Anglo-Nubiana e nos avinos. A variaçao inicial no ritmo respiratorio apresentou-se elevada na Anglo-Nubiana em comparaçao com as outras raças de caprinos e avinos. Depois do exercicio, os avinos apresentaram menoI elevaçao no ritmo respiratorio do que os caprinos. Isto pode explicar o grau de recuperaçao mais rapida da temperatura corporal dos caprinos Bhuj e Canindé, os quais tiveram distintamente os mais elevados ritmos respiratorios após o exercicio. 0 ritmo respiratório da Anglo-Nubiana voltou ao normal dentro de 15 minutas apos o exercicio; somente o da Bhuj continuou elevado após os 15 minutos de descanso. Todas as espécies voltaram ao ritmo respiratório normal, após os trinta minutos de descanso. [Heat tolerance of goats and woolless sheep in Sobral Brazil]