Study of Inhomogeneities in the Solar Atmosphere

We have analysed a large number of Ca II line profiles at the site of the bright points in the interior of the network using a 35-minute long time sequence spectra obtained at hte Vacuum Tower Telesope (VTT) of hte Sacramento Peak Observatory on a quiet region of the solar disc and studied the dynamical processes associated with these structures. Our analysis shows that the profiles can be grouped into three classes in terms of their evolutionary behavior. It is surmised that the differences in their behavior is directly linked with the inner network photospheric magnetic points to which they have been observed to bear a spatial correspondence. The light curves of these bright points give the impression that the"main pulse" which is the upward propagating disturbance carrying energy throws the medium within the bright point into a resonant mode of oscillation that are seen as the follower pulses. The main pulse as well as the follower pulses have identical periods of intensity oscillations, with a mean value around 190 ± 20 secs. We show that the energy transported by these main pulses at the sits of the bright points over the entire visible solar surface can account for a substantial freedom of the radiative loss from the quiet chromosphere according to current models

Intensity oscillations in coronal XBPs from Hinode/XRT observations

Our aim is to investigate the intensity oscillations in coronal X-ray Bright Points (XBPs). We analysed a 7-hours long time sequence of the soft X-ray images obtained on April 14, 2007 with 2-min cadence using X-Ray Telescope (XRT) on-board the Hinode mission. We use SSW in IDL to derive the time series of 14 XBPs and 2 background regions. For the first time, we have tried to use power spectrum analysis on XBPs data to determine the periods of intensity oscillations. coronal X-ray Bright Points (XBPs). The power spectra of XBPs show several significant peaks at different frequencies corresponding to a wide variety of time scales which range from a few minutes to hours. The light curves of all the XBPs give the impression that the XBPs can be grouped into three classes depending on emission levels: (i) weak XBPs; (ii) bright XBPs; and (iii) very strong XBPs. The periods of intensity oscillation are consistent in all the XBPs and are independent of their brightness level, suggesting that the heating mechanisms in all the three groups of XBPs are similar. The different classes of XBPs may be related to the different strengths of the magnetic field with which they have been associated.Comment: 7 pages, 3 figure

Nonlinear Force-Free Field Modeling of the Solar Magnetic Carpet and Comparison with SDO/HMI and Sunrise/IMaX Observations

In the quiet solar photosphere, the mixed polarity fields form a magnetic carpet, which continuously evolves due to dynamical interaction between the convective motions and magnetic field. This interplay is a viable source to heat the solar atmosphere. In this work, we used the line-of-sight (LOS) magnetograms obtained from the Helioseismic and Magnetic Imager (HMI) on the \textit{Solar Dynamics Observatory} (\textit{SDO}), and the Imaging Magnetograph eXperiment (IMaX) instrument on the \textit{Sunrise} balloon-borne observatory, as time dependent lower boundary conditions, to study the evolution of the coronal magnetic field. We use a magneto-frictional relaxation method, including hyperdiffusion, to produce time series of three-dimensional (3D) nonlinear force-free fields from a sequence of photospheric LOS magnetograms. Vertical flows are added up to a height of 0.7 Mm in the modeling to simulate the non-force-freeness at the photosphere-chromosphere layers. Among the derived quantities, we study the spatial and temporal variations of the energy dissipation rate, and energy flux. Our results show that the energy deposited in the solar atmosphere is concentrated within 2 Mm of the photosphere and there is not sufficient energy flux at the base of the corona to cover radiative and conductive losses. Possible reasons and implications are discussed. Better observational constraints of the magnetic field in the chromosphere are crucial to understand the role of the magnetic carpet in coronal heating.Comment: Accepted for publication in The Astrophysical Journal (13 pages, 10 figures

Cheilolejeunea obtusifolia (Lejeuneaceae) new to the Indian mainland from the Western Ghats

Cheilolejeunea obtusifolia, so far known only from Andaman Islands in India, is added here to the flora of the Indian mainland from the Anamalais in the Western Ghats. A brief description with an illustration and a photoplate is provided here since there is none based on any Indian material

Ceratolejeunea belangeriana (Lejeuneaceae), new to India from the Western Ghats

Abstract Ceratolejeunea belangeriana is added here to the liverwort flora of India from the Indira Gandhi National Park, Anamalais in the Western Ghats. A brief description together with illustrations are provided

Additions to the moss flora of peninsular India from the Western Ghats

Two Asian mosses Entodontopsis setschwanica (Broth.) W. R. Buck et R. R. Ireland and Mitthyridium cardotii (M. Fleisch.) H. Rob., so far known from the Eastern Himalaya and Northeast India, respectively for India, are added here to the moss flora of Peninsular India from the Western Ghats. Brief descriptions with illustrations are provided

Genus Wijkia (Sematophyllaceae, Bryophyta) in the western ghats of India

The Asian moss Wijkia baculifera (Dixon) H. A. Crum so far known from Northeast India and Myanmar, is added here to the moss flora of Peninsular India from the Western Ghats. A brief description with illustrations and photographic plate is provided

Dynamics of the solar magnetic bright points derived from their horizontal motions

The sub-arcsec bright points (BP) associated with the small scale magnetic fields in the lower solar atmosphere are advected by the evolution of the photospheric granules. We measure various quantities related to the horizontal motions of the BPs observed in two wavelengths, including the velocity auto-correlation function. A 1 hr time sequence of wideband H$\alpha$ observations conducted at the \textit{Swedish 1-m Solar Telescope} (\textit{SST}), and a 4 hr \textit{Hinode} \textit{G}-band time sequence observed with the Solar Optical telescope are used in this work. We follow 97 \textit{SST} and 212 \textit{Hinode} BPs with 3800 and 1950 individual velocity measurements respectively. For its high cadence of 5 s as compared to 30 s for \textit{Hinode} data, we emphasize more on the results from \textit{SST} data. The BP positional uncertainty achieved by \textit{SST} is as low as 3 km. The position errors contribute 0.75 km$^2$ s$^{-2}$ to the variance of the observed velocities. The \textit{raw} and \textit{corrected} velocity measurements in both directions, i.e., $(v_x,v_y)$, have Gaussian distributions with standard deviations of $(1.32,1.22)$ and $(1.00, 0.86)$ km s$^{-1}$ respectively. The BP motions have correlation times of about $22 - 30$ s. We construct the power spectrum of the horizontal motions as a function of frequency, a quantity that is useful and relevant to the studies of generation of Alfv\'en waves. Photospheric turbulent diffusion at time scales less than 200 s is found to satisfy a power law with an index of 1.59.Comment: Accepted for publication in The Astrophysical Journal. 24 pages, 9 figures, and 1 movie (not included

Rediscovery of a long-lost moss Fissidens serratus var. serratus in the Western Ghats of India

Fissidens serratus, a long-lost liverwort, is rediscovered in the Indira Gandhi National Park in Anamalais in the Western Ghats in Peninsular India after nearly two centuries. Till now, the collection made by Perrottet between 1834 and 1839 in the Nilgiri Hills has been the only Indian representative of this species