Oscillations in active region fan loops: Observations from EIS/{\it Hinode} and AIA/SDO

Active region fan loops in AR 11076 were studied, in search of oscillations, using high cadence spectroscopic observations from EIS on board Hinode combined with imaging sequences from the AIA on board SDO. Spectra from EIS were analyzed in two spectral windows, \FeXII 195.12 \AA and \FeXIII 202.04 \AA along with the images from AIA in 171 \AA and 193 \AA channels. We find short ($<$3 min) and long ($\approx$9 min) periods at two different locations. Shorter periods show oscillations in all the three line parameters and the longer ones only in intensity and Doppler shift but not in line width. Line profiles at both these locations do not show any visible blue-shifted component and can be fitted well with a single Gaussian function along with a polynomial background. Results using co-spatial and co-temporal data from AIA/SDO do not show any significant peak corresponding to shorter periods, but longer periods are clearly observed in both 171 \AA and 193 \AA channels. Space-time analysis in these fan loops using images from AIA/SDO show alternate slanted ridges of positive slope, indicative of outward propagating disturbances. The apparent propagation speeds were estimated to be 83.5 $\pm$ 1.8 \kms and 100.5 $\pm$ 4.2 \kms, respectively, in the 171 \AA and 193 \AA channels. Observed short period oscillations are suggested to be caused by the simultaneous presence of more than one MHD mode whereas the long periods are suggested as signatures of slow magneto-acoustic waves. In case of shorter periods, the amplitude of oscillation is found to be higher in EIS lines with relatively higher temperature of formation. Longer periods, when observed from AIA, show a decrease of amplitude in hotter AIA channels which might indicate damping due to thermal conduction owing to their acoustic nature.Comment: Accepted for publication in Solar Physic

Frequency-dependent damping in propagating slow magneto-acoustic waves

Propagating slow magneto-acoustic waves are often observed in polar plumes and active region fan loops. The observed periodicities of these waves range from a few minutes to few tens of minutes and their amplitudes were found to decay rapidly as they travel along the supporting structure. Previously, thermal conduction, compressive viscosity, radiation, density stratification, and area divergence, were identified to be some of the causes for change in the slow wave amplitude. Our recent studies indicate that the observed damping in these waves is frequency dependent. We used imaging data from SDO/AIA, to study this dependence in detail and for the first time from observations we attempted to deduce a quantitative relation between damping length and frequency of these oscillations. We developed a new analysis method to obtain this relation. The observed frequency dependence does not seem to agree with the current linear wave theory and it was found that the waves observed in the polar regions show a different dependence from those observed in the on-disk loop structures despite the similarity in their properties.Comment: accepted for publication in Ap

Management of Potato Nematodes:An overview

Root-knot nematodes and cyst nematodes are important constraints that reduce potato yields in India. Three species of Meloidogyne cause root-knots on the crop throughout the country, of which, M. incognita is more wide-spread. Infected tubers also result in marketable-yield-loss particularly in the seed potatoes. The cyst nematodes include two species of Globodera restricted to the hilly regions of Tamil Nadu and are of quarantine importance, inhibiting seedpotato production. Potato produce from these hills is used only for consumption. The endoparasitic nature of their life cycle, deposition of eggs into a gelatinous egg mass in root knot and the female turning in to a hard cyst encompassing the eggs within them in cyst nematode makes them difficult organisms to manage. Both these nematodes exhibit physiologic variation, hence, their management is not absolute with host-resistance. Therefore, an Integrated Nematode Management (INM) is adopted in both the cases. Root-knot nematode in North India is managed using nematode-free seed tubers, crop rotation with maize or wheat and application of 1-2 kg ai /ha Carbofuran 3% G at the time of potato planting. Cyst nematode in Tamil Nadu hills is managed by crop rotation with vegetables, particularly cabbage and carrot, intercropping potato with beans or wheat, alternating nematode resistant potato variety 'Kufri Swarna' and application of 2 kg ai /ha Carbofuran 3% G at planting. A two-year adoption of INM for root-knot and a three-year INM practice for cyst nematodes gives efficient and economical production system. Potato farmers in Himachal Pradesh and Tamil Nadu hills follow practices standardized at the Central Potato Research Institute, Shimla and it's substation in the Nilgiri hills

Propagating Disturbances along fan-like coronal loops in an active region

Propagating disturbances are often observed in active region fan-like coronal loops. They were thought to be due to slow mode MHD waves based on some of the observed properties. But the recent studies involving spectroscopy indicate that they could be due to high speed quasi-periodic upflows which are difficult to distinguish from upward propagating slow waves. In this context, we have studied a fan loop structure in the active region AR 11465 using simultaneous spectroscopic and imaging observations from Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode and Atmospheric Imaging Assembly (AIA) on board SDO. Analysis of the data shows significant oscillations at different locations. We explore the variations in different line parameters to determine whether the waves or flows could cause these oscillations to improve the current understanding on the nature of these disturbances.Comment: 12 pages, 6 figures. Accepted for publication in RA

Omnipresent long-period intensity oscillations in open coronal structures

Quasi-periodic propagating disturbances in coronal structures have been interpreted as slow magneto-acoustic waves and/or periodic upflows. Here we aim to understand their nature from the observed properties using a three-hour imaging sequence from AIA/SDO in two different temperature channels. We also compare the characteristics with a simple wave model. We searched for propagating disturbances in open-loop structures at three different locations; a fan loop-structure off-limb, an on-disk plume-like structure and the plume/interplume regions in the north pole of the sun. In each of the subfield regions chosen to cover these structures, the time series at each pixel location was subjected to wavelet analysis to find the different periodicities. We then constructed powermaps in three different period ranges. We also constructed space-time maps for the on-disk plume structure to estimate the propagation speeds in different channels. We find propagating disturbances in all three structures. Powermaps indicate that the power in the long-period range is significant up to comparatively longer distances along the loop than that in the shorter periods. This nature is observed in all three structures. A detailed analysis on the on-disk plume structure gives consistently higher propagation speeds in the 193 \AA channel and also reveals spatial damping along the loop. The amplitude and the damping length values are lower in hotter channels, indicating their acoustic dependence. These properties can be explained very well with a propagating slow-wave model. We suggest that these disturbances are more likely to be caused by propagating slow magneto-acoustic waves than by high-speed quasi-periodic upflows. We find that intensity oscillations in longer periods are omnipresent at larger heights even in active regions.Comment: accepted for publication in A &

The topology of the P-T diagram of DOBBCA in the vicinity of the reentrant nematic-smectic C-smectic A multicritical point

The P-T diagram of 4(4-n-decyloxybenzoyloxy)-benzylidene-4'-cyanoanihe shows a new kind of multicriticd point, viz., a reentrant nematic-smectic C-smectic A point, at 0.55 ± 0.01 kbar and 86.8 ± 0.1° C. The topology of the diagram close to this point has been studied using precise optical hgh pressure techniques