Author name code: bharti ADS astronomy entries on 2022-09-14 author:"Bharti, Lokesh" ------------------------------------------------------------------------ Title: Variation in cosmic ray flux during Solar Eclipse on 21 June, 2020 at Jaipur, India Authors: Pandya, Aalok; Gupta, S. K.; Meena, Dalpat; Bharti, Lokesh Bibcode: 2022APh...13602659P Altcode: Variation in gamma ray flux was recorded during the Annular Solar Eclipse on 21 June, 2020 at Jaipur, India where 88.3% of the solar disk was eclipsed. Two Sodium Iodide NaI (Tl) scintillation detectors were employed for the experiment and flux was recorded in the energy range 300 keV to 2 MeV. The first detector employed to record data for the duration of 3 h and 30 min records a sizeable enhancement at the characteristic energy 1460 keV and the corresponding single escape peak at 949 keV. No substantial variation in the radiations was noticed by the detector employed for recording data for 20 critical minutes during the peak of the eclipse. Title: Chromospheric plasma ejection above a pore Authors: Bharti, L.; Sobha, B.; Quintero Noda, C.; Joshi, C.; Pandya, U. Bibcode: 2020MNRAS.493.3036B Altcode: 2020arXiv200204503B We present high spatial resolution observations of short-lived transients, ribbons and jet-like events above a pore in Ca II H images where fine structure, like umbral dots, light bridges and penumbral microfilaments, is present in the underlying photosphere. We found that current layers are formed at the edges of the convective fine structure, due to the shear between their horizontal field and the ambient vertical field. High vertical electric current density patches are observed in the photosphere around these events, which indicates the formation of a current sheet at the reconnection site. In the framework of past studies, low altitude reconnection could be the mechanism that produces such events. The reconnection is caused by an opposite polarity field produced by the bending of field lines by convective downflows at the edge of pore fine structure. Title: Opposite Polarity Magnetic Fields and Convective Downflows in a Simulated Sunspot Penumbra Authors: Bharti, Lokesh; Rempel, Matthias Bibcode: 2019ApJ...884...94B Altcode: 2019arXiv190806439B Recent numerical simulations and observations of sunspots show a significant amount of opposite polarity magnetic fields within the sunspot penumbra. Most of the opposite polarity fields are associated with convective downflows. We present an analysis of 3D MHD simulations through forward modeling of synthetic Stokes profiles of the Fe I 6301.5 Å and Fe I 6302.5 Å lines. The synthetic Stokes profiles are spatially and spectrally degraded considering typical instrument properties. Line bisector shifts of the Fe I 6301.5 Å line are used to determine line-of-sight velocities. Far wing magnetograms are constructed from the Stokes V profiles of the Fe I 6302.5 Å line. While we find an overall good agreement between observations and simulations, the fraction of opposite polarity magnetic fields, the downflow filling factor, and the opposite polarity-downflow association are strongly affected by spatial smearing and presence of strong gradients in the line-of-sight magnetic fields and velocity. A significant fraction of opposite polarity magnetic fields and downflows is hidden in the observations due to typical instrumental noise. Comparing simulations that differ by more than a factor of two in grid spacing, we find that these quantities are robust within the simulations. Title: Small-Scale Activity Above the Penumbra of a Fast-Rotating Sunspot Authors: Bharti, L.; Quintero Noda, C.; Rakesh, S.; Sobha, B.; Pandya, A.; Joshi, C. Bibcode: 2018SoPh..293...46B Altcode: High-resolution observations of small-scale activity above the filamentary structure of a fast-rotating sunspot of NOAA Active Region 10930 are presented. The penumbral filament that intrudes into the umbra shows a central dark core and substructures. It almost approached another end of the umbra, like a light bridge. The chromospheric Ca II H images show many jet-like structures with a bright leading edge above it. These bright jets move across the filament tips and show coordinated up and down motions. Transition region images also show brightening at the same location above the intrusion. Coronal 195 Å images suggest that one end of the bright coronal loop footpoints resides in this structure. The intrusion has opposite polarity with respect to the umbra. Strong downflows are observed at the edges along the length of the intrusion where the opposite-polarity field is enhanced. We also observe a counter-Evershed flow in the filamentary structure that also displays brightening and energy dissipation in the upper atmosphere. This scenario suggests that the jets and brightenings are caused by low-altitude reconnection driven by opposite-polarity fields and convective downflows above such structures. Title: Lambda-shaped jets from a penumbral intrusion into a sunspot umbra: a possibility for magnetic reconnection Authors: Bharti, L.; Solanki, S. K.; Hirzberger, J. Bibcode: 2017A&A...597A.127B Altcode: We present the results of high resolution co-temporal and co-spatial photospheric and chromospheric observations of sunspot penumbral intrusions. The data were taken with the Swedish Solar Telescope (SST) on the Canary Islands. Time series of Ca II H images show a series of transient jets extending roughly 3000 km above a penumbral intrusion into the umbra. For most of the time series, jets were seen along the whole length of the intruding bright filament. Some of these jets develop a clear λ-shaped structure, with a small loop appearing at their footpoint and lasting for around a minute. In the framework of earlier studies, the observed transient λ shape of these jets suggests that they could be caused by magnetic reconnection between a curved arcade-like or flux rope-like field in the lower part of the penumbral intrusion and the more vertical umbral magnetic field forming a cusp-shaped structure above the penumbral intrusion.

Movies associated to Figs. 1 and 2 are available at http://www.aanda.org Title: Fine structures at pore boundary Authors: Bharti, L.; Quintero Noda, C.; Joshi, C.; Rakesh, S.; Pandya, A. Bibcode: 2016MNRAS.462L..93B Altcode: We present high resolution observations of fine structures at pore boundaries. The inner part of granules towards umbra show dark striations which evolve into a filamentary structure with dark core and `Y' shape at the head of the filaments. These filaments migrate into the umbra similar to penumbral filaments. These filaments show higher temperature, lower magnetic field strength and more inclined field compared to the background umbra. The optical depth stratification of physical quantities suggests their similarity with penumbral filaments. However, line-of-sight velocity pattern is different from penumbral filaments where they show downflows in the deeper layers of the atmosphere while the higher layers show upflows. These observations show filamentation in a simple magnetic configuration. Title: Magnetic reconnection as a source of jets from a penumbral intrusion into a sunspot umbra Authors: Bharti, L.; Solanki, S. K.; Hirzberger, J. Bibcode: 2015arXiv150902123B Altcode: We present the results of high resolution co-temporal and co-spatial photospheric and chromospheric observations of sunspot penumbral intrusions. The data was taken with the Swedish Solar Telescope (SST) on the Canary Islands. Time series of Ca\,II H images show a series of transient jets extending roughly 3000 km above a penumbral intrusion into the umbra. For most of the time series jets were seen along the whole length of the intruding bright filament. Some of these jets develop a clear $\lambda$-shaped structure, with a small loop appearing at their footpoint and lasting for around a minute. In the framework of earlier studies, the observed transient $\lambda$ shape of these jets strongly suggests that they are caused by magnetic reconnection between a curved arcade-like or flux-rope like field in the lower part of the penumbral intrusion and the more vertical umbral magnetic field forming a cusp-shaped structure above the penumbral intrusion. Title: Fine structure above a light bridge in the transition region and corona Authors: Bharti, L. Bibcode: 2015MNRAS.452L..16B Altcode: 2015arXiv150502412B We present the results of multiwavelength, co-spatial and near co-temporal observations of jets above a sunspot light bridge (LB). The data were obtained with the Solar Optical Telescope on board Hinode, the Interface Region Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory. Most of the jets in the Ca II H images show decreasing brightness with height while in the IRIS slit-jaw images at 1330 Å jets show a bright leading edge. These jets show rising and falling motion as evident from the parabolic profile obtained from the time-distance diagram. The rising and falling speeds of the jets are similar. These jets show a coordinated behaviour between neighbouring jets moving jointly up and down. Some of the jets show a plasma ejection from the leading edge which is also hotter at the transition region (TR) and coronal temperatures. A similar behaviour is seen in the AIA wavebands that suggests that jets above the LB reach up to the lower corona and the leading edges are heated up to coronal temperatures. Such jets are important means of transfer mass and energy to the TR and corona above sunspots. Title: Fine structures in the atmosphere above a sunspot umbra Authors: Bharti, L.; Hirzberger, J.; Solanki, S. K. Bibcode: 2013A&A...552L...1B Altcode: 2013arXiv1302.2772B We present simultaneous photospheric and chromospheric observations of the trailing sunspot in NOAA 10904, obtained with the Swedish Solar Telescope (SST) La Palma, Canary Islands. Time series of high resolution Ca ii H images show transient jet-like structures in sunspot umbrae are elongated, which we call umbral microjets. These jets are directed roughly parallel to nearby penumbral microjets, suggesting that they are aligned with the background magnetic field. In general, first a bright dot-like structure appears, from which a jet later emerges, although some jets appear without an associated chromospheric dot. Bright photospheric umbral dots are associated with umbral microjets arising in the outer umbra. Nevertheless, a one-to-one correspondence between jet-like events and underlying umbral dots is not seen. They are typically less than 1'' long and less than 0.3 arcsec wide. The typical lifetime of umbral microjets is around one minute. The brightness of these structures increases from the center of the umbra toward the umbra-penumbra boundary along with the brightness of the local background. Title: Observational study of an eruptive event in vicinity of umbral bright features Authors: Joshi, Chandan; Jaaffrey, S. N. A.; Bharti, Lokesh Bibcode: 2012cosp...39..846J Altcode: 2012cosp.meet..846J The solar chromosphere is very dynamic. The magnetic field and waves play the important role in eruptive events in chromosphere on different spatial and temporal scales. With the increase in the observational capabilities with Hinode the diagnostic of chromosphere can be improved. We present here the observations of eruptive event in the vicinity of umbral bright features with the help of SOT on board Hinode. Title: Waves as the Source of Apparent Twisting Motions in Sunspot Penumbrae Authors: Bharti, L.; Cameron, R. H.; Rempel, M.; Hirzberger, J.; Solanki, S. K. Bibcode: 2012ApJ...752..128B Altcode: 2012arXiv1204.2221B The motion of dark striations across bright filaments in a sunspot penumbra has become an important new diagnostic of convective gas flows in penumbral filaments. The nature of these striations has, however, remained unclear. Here, we present an analysis of small-scale motions in penumbral filaments in both simulations and observations. The simulations, when viewed from above, show fine structure with dark lanes running outward from the dark core of the penumbral filaments. The dark lanes either occur preferentially on one side or alternate between both sides of the filament. We identify this fine structure with transverse (kink) oscillations of the filament, corresponding to a sideways swaying of the filament. These oscillations have periods in the range of 5-7 minutes and propagate outward and downward along the filament. Similar features are found in observed G-band intensity time series of penumbral filaments in a sunspot located near disk center obtained by the Broadband Filter Imager on board the Hinode. We also find that some filaments show dark striations moving to both sides of the filaments. Based on the agreement between simulations and observations we conclude that the motions of these striations are caused by transverse oscillations of the underlying bright filaments. Title: Can Overturning Motions in Penumbral Filaments BE Detected? Authors: Bharti, Lokesh; Schuessler, Manfred; Rempel, Matthias Bibcode: 2011sdmi.confE..79B Altcode: Numerical simulations indicate that the filamentation of sunspot penumbrae and the associated systematic outflow (the Evershed effect) are due to convectively driven fluid motions constrained by the inclined magnetic field. We investigate whether these motions, in particular the upflows in the bright filaments and the downflows at their edges, can be reliably observed with existing instrumentation. We use a snapshot from a sunspot simulation to calculate two-dimensional maps of synthetic line profiles for the spectral lines Fe I 7090.4 Å and C I 5380.34 Å. The maps are spatially and spectrally degraded according to typical instrument properties. Line-of-sight velocities are determined from line bisector shifts. We find that the detectability of the convective flows is strongly affected by spatial smearing, particularly so for the downflows. Furthermore, the line-of-sight velocities are dominated by the Evershed flow unless the observation is made very near the disk center. These problems may have compromised recent attempts to detect overturning penumbral convection. Lines with a low formation height are best suited for detecting the convective flows. Title: Can Overturning Motions in Penumbral Filaments Be Detected? Authors: Bharti, Lokesh; Schüssler, Manfred; Rempel, Matthias Bibcode: 2011ApJ...739...35B Altcode: 2011arXiv1107.0398B Numerical simulations indicate that the filamentation of sunspot penumbrae and the associated systematic outflow (the Evershed effect) are due to convectively driven fluid motions constrained by the inclined magnetic field. We investigate whether these motions, in particular the upflows in the bright filaments and the downflows at their edges, can be reliably observed with existing instrumentation. We use a snapshot from a sunspot simulation to calculate two-dimensional maps of synthetic line profiles for the spectral lines Fe I 7090.4 Å and C I 5380.34 Å. The maps are spatially and spectrally degraded according to typical instrument properties. Line-of-sight velocities are determined from line bisector shifts. We find that the detectability of the convective flows is strongly affected by spatial smearing, particularly so for the downflows. Furthermore, the line-of-sight velocities are dominated by the Evershed flow unless the observation is made very near the disk center. These problems may have compromised recent attempts to detect overturning penumbral convection. Lines with a low formation height are best suited for detecting the convective flows. Title: Probing the Role of Magnetic-Field Variations in NOAA AR 8038 in Producing a Solar Flare and CME on 12 May 1997 Authors: Jain, Rajmal; Awasthi, Arun K.; Chandel, Babita; Bharti, Lokesh; Hanaoka, Y.; Kiplinger, A. L. Bibcode: 2011SoPh..271...57J Altcode: 2011SoPh..tmp..127J; 2011SoPh..tmp..182J; 2011SoPh..tmp..251J; 2011arXiv1106.2702J We carried out a multi-wavelength study of a Coronal Mass Ejection (CME) and an associated flare, occurring on 12 May 1997. We present a detailed investigation of magnetic-field variations in NOAA Active Region 8038 which was observed on the Sun during 7 - 16 May 1997. This region was quiet and decaying and produced only a very small flare activity during its disk passage. However, on 12 May 1997 it produced a CME and associated medium-size 1B/C1.3 flare. Detailed analyses of Hα filtergrams and SOHO/MDI magnetograms revealed continual but discrete surge activity, and emergence and cancellation of flux in this active region. The movie of these magnetograms revealed the two important results that the major opposite polarities of pre-existing region as well as in the emerging-flux region were approaching towards each other and moving magnetic features (MMF) were ejected from the major north polarity at a quasi-periodicity of about ten hours during 10 - 13 May 1997. These activities were probably caused by magnetic reconnection in the lower atmosphere driven by photospheric convergence motions, which were evident in magnetograms. The quantitative measurements of magnetic-field variations such as magnetic flux, gradient, and sunspot rotation revealed that in this active region, free energy was slowly being stored in the corona. Slow low-layer magnetic reconnection may be responsible for the storage of magnetic free energy in the corona and the formation of a sigmoidal core field or a flux rope leading to the eventual eruption. The occurrence of EUV brightenings in the sigmoidal core field prior to the rise of a flux rope suggests that the eruption was triggered by the inner tether-cutting reconnection, but not the external breakout reconnection. An impulsive acceleration, revealed from fast separation of the Hα ribbons of the first 150 seconds, suggests that the CME accelerated in the inner corona, which is also consistent with the temporal profile of the reconnection electric field. Based on observations and analysis we propose a qualitative model, and we conclude that the mass ejections, filament eruption, CME, and subsequent flare were connected with one another and should be regarded within the framework of a solar eruption. Title: Evidence for Convection in Sunspot Penumbrae Authors: Bharti, L.; Solanki, S. K.; Hirzberger, J. Bibcode: 2010ApJ...722L.194B Altcode: 2010arXiv1009.2919B We present an analysis of twisting motions in penumbral filaments in sunspots located at heliocentric angles from 30° to 48° using three time series of blue continuum images obtained by the Broadband Filter Imager (BFI) on board Hinode. The relations of the twisting motions to the filament brightness and the position within the filament and within the penumbra, respectively, are investigated. Only certain portions of the filaments show twisting motions. In a statistical sense, the part of the twisting portion of a filament located closest to the umbra is brightest and possesses the fastest twisting motion, with a mean twisting velocity of 2.1 km s-1. The middle and outer sections of the twisting portion of the filament (lying increasingly further from the umbra), which are less bright, have mean velocities of 1.7 km s-1 and 1.35 km s-1, respectively. The observed reduction of brightness and twisting velocity toward the outer section of the filaments may be due to reducing upflow along the filament's long axis. No significant variation of twisting velocity as a function of viewing angles was found. The obtained correlation of brightness and velocity suggests that overturning convection causes the twisting motions observed in penumbral filament and may be the source of the energy needed to maintain the brightness of the filaments. Title: Properties of simulated sunspot umbral dots Authors: Bharti, L.; Beeck, B.; Schüssler, M. Bibcode: 2010A&A...510A..12B Altcode: 2009arXiv0911.5068B Realistic 3D radiative MHD simulations reveal the magneto-convective processes underlying the formation of the photospheric fine structure of sunspots, including penumbral filaments and umbral dots. Here we provide results from a statistical analysis of simulated umbral dots and compare them with reports from high-resolution observations. A multi-level segmentation and tracking algorithm has been used to isolate the bright structures in synthetic bolometric and continuum brightness images. Areas, brightness, and lifetimes of the resulting set of umbral dots are found to be correlated: larger umbral dots tend to be brighter and live longer. The magnetic field strength and velocity structure of umbral dots on surfaces of constant optical depth in the continuum at 630 nm indicate that the strong field reduction and high velocities in the upper parts of the upflow plumes underlying umbral dots are largely hidden from spectro-polarimetric observations. The properties of the simulated umbral dots are generally consistent with the results of recent high-resolution observations. However, the observed population of small, short-lived umbral dots is not reproduced by the simulations, possibly owing to insufficient spatial resolution. Title: Fine Structure of Chromospheric Brightenings above a Light Bridge and Penumbral Filaments Authors: Bharti, Lokesh Bibcode: 2010cosp...38.2848B Altcode: 2010cosp.meet.2848B We present simultaneous photospheric and chromospheric observations of the trailing sunspot in NOAA 10904. At the limit of the instrumental spatial resolution Ca II H images show jet-like brightenings above a lightbridge and a penumbral filament that intrudes into the umbra. The observations were carried out with the Swedish Solar Telescope (SST) on 13 August 2006. The Solar Optical Universal Polarimeter (SOUP) filter was used to scan the Fe I 6302.5 ˚ line at A 6 wavelength positions. Full Stokes polarimetry was performed and the magnetic field vector was obtained by means of a Milne-Eddington inversion of the radiative transfer equation. The data reveal a more inclined field in the light bridge and penumbral filament than in the umbra with a vertical current density higher than 200 mA m-2 . Also opposite polarity patches were found in the light bridge. Such a magnetic configuration indicates low altitude reconnection. A similar mechanism causes penumbral microjets which were also observed along other penumbral filaments. Title: Spectropolarimetery of umbral fine structures from Hinode: evidence for magnetoconvection Authors: Bharti, Lokesh; Joshi, Chandan; Jaaffrey, S. N. A.; Jain, Rajmal Bibcode: 2009MNRAS.393...65B Altcode: 2008arXiv0811.1722B We present spectropolarimetric analysis of umbral dots and a light bridge fragment that show dark lanes in G-band images. Umbral dots show upflow as well as associated positive Stokes V area asymmetry in their central parts. Larger umbral dots show downflow patches in their surrounding parts that are associated with negative Stokes V area asymmetry. Umbral dots show weaker magnetic field in central part and higher magnetic field in peripheral area. Umbral fine structures are much better visible in total circularly polarized light than in continuum intensity. Umbral dots show a temperature deficit above dark lanes. The magnetic field inclination shows a cusp structure above umbral dots and a light bridge fragment. We compare our observational findings with 3D magnetohydrodynamic simulations. Title: A High Resolution Study of Umbral Flashes and Running Penumbral Waves using Hinode Observations Authors: Joshi, C.; Bharti, L.; Jaaffrey, S. N. A. Bibcode: 2008ESPM...12.2.27J Altcode: We present a study of intensity oscillations in sunspots using high resolution ( temporal and spatial) CaII H data and Gband data from Hinode. The intensity variations show increased power at 5.5mHz in umbra and frequency decreases as we move towards penumbra and outwards. An attempt was also made to find any relationship between the dark umbra and oscillation power and umbral fine structure and oscillation power but no obious relation could be established. Title: Spectropolarimetery of Umbral Fine Structures from Hinode: Evidence for Magnetoconvection Authors: Bharti, L.; Joshi, C.; Jaaffrey, S. N. A. Bibcode: 2008ESPM...12..2.7B Altcode: We present spectropolarimetric analysis of umbral dots and light bridge fragment that show dark lanes in G-band images. Umbral dots show upflow as well as associated positive stokes V area asymmetry in central part. Bigger umbral dots show down flow patches in surrounding part that associated with negative stokes V area asymmetry.

Umbral dots show weaker magnetic field in central part and higher magnetic field in peripheral area. Umbral fine structures are much clear in total circular polarization as compared to continuum intensity. Umbral dots show temperature deficit above dark lanes. Magnetic field inclination show cusp above umbral dots and light bridge fragment. We compare our observational findings with 3D magnetohydrodynamic simulations. Title: Enhanced Joule Heating in Umbral Dots Authors: Joshi, Chandan; Bharti, Lokesh; Jaaffrey, S. N. A. Bibcode: 2008cosp...37.1411J Altcode: 2008cosp.meet.1411J We present a study of magnetic fields in umbral dots (UDs) and its consequences on the Joule heating of the UDs. Hamedivafa (2003) studied the Joule heating using the vertical component of the magnetic field. In this paper the magnetic field profile in the UDs is investigated including a new azimuthal component of the magnetic field which might explain a relatively large enhancement of Joule heating causing higher brightness near the circumference of the UDs. Title: A High resolution study of Umbral Flashes and Running penumbral waves Authors: Joshi, Chandan; Bharti, Lokesh; Jaaffrey, S. N. A. Bibcode: 2008cosp...37.1410J Altcode: 2008cosp.meet.1410J We present a study of intensity oscillations in sunspots using high resolution ( temporal and spatial) CaII H data and Gband data from Hinode. The intensity variations show increased power at 5.5mHz in umbra and at 3.3mHz in penumbra. We also found that umbra does not oscillate as a single element at above mentioned freqencies but there are several elements in different phases, penumbra seems to oscillate as a whole in same phase. An attempt was also made to find any relationship between Gband mean intensity and oscillation power. Title: Observations of Dark Lanes in Umbral Fine Structure from the Hinode Solar Optical Telescope: Evidence for Magnetoconvection Authors: Bharti, Lokesh; Joshi, Chandan; Jaaffrey, S. N. A. Bibcode: 2007ApJ...669L..57B Altcode: An analysis of high-resolution G-band images of active region NOAA 10930 is presented. The observations were recorded with the Broadband Filter Imager (BFI) attached to the Solar Optical Telescope (SOT) on board the Hinode mission. We observed dark lanes in umbral dots up to six folds in larger ones. Formation of umbral dots from dark core penumbral filament shows dark lanes. The evolution of the light bridge from the dark core penumbral filament is observed, which further disintegrates into umbral dots. These observations are compatible with the simulations of three-dimensional radiative magnetoconvection with gray radiative transfer in sunspot umbra by Schüssler & Vögler, which support the notion that these structures appear as a result of magnetoconvection. Title: Enhanced Joule Heating in Umbral Dots Authors: Joshi, Chandan; Bharti, Lokesh; Jaaffrey, S. N. A. Bibcode: 2007SoPh..245..239J Altcode: 2007arXiv0705.1141J We present a study of magnetic fields in umbral dots (UDs) and its consequences on the Joule heating of the UDs. Hamedivafa (Astron. Astrophys.407, 761, 2003) studied the Joule heating using the vertical component of the magnetic field. In this paper the magnetic field profile in the UDs is investigated by including a new azimuthal component of the magnetic field that might explain a relatively large enhancement of Joule heating causing higher brightness near the circumference of the UDs. Title: Evidence for Magnetoconvection in Sunspot Umbral Dots Authors: Bharti, Lokesh; Jain, Rajmal; Jaaffrey, S. N. A. Bibcode: 2007ApJ...665L..79B Altcode: An analysis of high-resolution Dopplergrams and continuum images of NOAA AR 8350 is presented. The observations were recorded with the universal birefringent filter attached to the Dunn Solar Telescope at the National Solar Observatory, Sunspot, New Mexico. We find upward velocity of the order of 400 m s-1 within umbral dots, surrounded by downward velocity of the order of 300 m s-1. This observation is compatible with the simulations of three-dimensional radiative magnetoconvection with gray radiative transfer in sunspot umbra by Schüssler & Vögler, which support the idea that umbral dots appear as a result of magnetoconvection. Title: Detection of opposite polarities in a sunspot light bridge: evidence of low-altitude magnetic reconnection Authors: Bharti, Lokesh; Rimmele, Thomas; Jain, Rajmal; Jaaffrey, S. N. A.; Smartt, R. N. Bibcode: 2007MNRAS.376.1291B Altcode: 2007astro.ph..1674B; 2007MNRAS.tmp..160B A multiwavelength photometric analysis was performed in order to study the sub-structure of a sunspot light bridge in the photosphere and the chromosphere. Active region NOAA 8350 was observed on 1998 October 8. The data consist of a 100 min time series of 2D spectral scans of the lines FeI 5576 Å, Hα 6563 Å, FeI 6302.5 Å, and continuum images at 5571 Å. We recorded line-of-sight magnetograms in 6302.5 Å. The observations were taken at the Dunn Solar Telescope at US National Solar Observatory, Sacramento Peak. We find evidence for plasma ejection from a light bridge followed by Ellerman bombs. Magnetograms of the same region reveal opposite polarity in light bridge with respect to the umbra. These facts support the notion that low-altitude magnetic reconnection can result in the magnetic cancellation as observed in the photosphere. Title: MHD Waves Observed in Isolated Bright Points Authors: Bharti, L.; Jain, R.; Joshi, C.; Jaaffrey, S. N. A. Bibcode: 2006ASPC..354...13B Altcode: We examine oscillations in three isolated bright points co-temporal and co-spatial in the photosphere and chromosphere in the G-band and Ca IIK line. Wavelet analysis was performed to study waves packets of traveling magnetohydrodynamic waves. In general, it is thought likely that the photosphere oscillates in response to granular buffeting, but it is also influenced strongly by the presence of magnetic fields. The observed oscillations reveal evidence for kink-mode waves, traveling up through the chromosphere and coupling with sausage-modes waves. This provides a means for energy deposition in the upper chromosphere. Title: G-Band Bright Points and Photospheric Magnetic Fields Authors: Bharti, L.; Jain, R.; Joshi, C.; Jaaffrey, S. N. A. Bibcode: 2006ASPC..358...61B Altcode: We present high resolution observations of magnetic flux concentrations within a decaying active region near disk center. We recorded G-band images, magnetograms, 2D spectral scan, and continuum images using the Universal Birefringent Filter at the Dunn Solar Telescope. The main results can be summarized as follows: The large-scale pattern of G-band bright points flux in plages are highly correlated, on sub-arcsecond scales; G-band bright points are cospatial and comorphous, with magnetic elements in intergranular lanes. Magnetic elements are continually advected into micropores by the photospheric flow field. We observed narrow (<0.25 arcsec) channels or sheets of downflowing plasma around bright points and micropores. This downflowing plasma shows accelerating nature in deeper layers of solar atmosphere. Upflow and downflow events are found within bright points while micropores show upflow. We compare our results with theoretical model predictions. Title: Intensity and Velocity Oscillations in Magnetic Flux Concentrations (P9) Authors: Bharti, L.; Rimmele, Thomas Bibcode: 2006ihy..workE.101B Altcode: We analyzed intensity and velocity oscillations in magnetic network using high-resolution 2D spectral scan images from Interferometric Bi- dimensional Spectrometer (IBIS). In photosphere, oscillations in intensity and velocity in 2-5.2 mHz band shows reduced amplitude while at higher frequencies 5.2-7.0 mHz and 7.3-25.8 mHz band oscillations amplitude enhance in line core intensity and shows reduced amplitude in line core velocity however in chromosphere the oscillations have different character, we found higher power in 2-5.2 mHz, 5.2-7.0 mHz and 7.3-25.8 mHz band in core velocity compared to core intensity. Amplitude variation with height is also inferred from our analysis. These findings are manifestation of high frequencies halos around strong flux concentrations (pores) in intermediate field strength network and mode conversion of solar p-modes in magnetic fields. Title: Plasma Flow In And Around Magnetic Flux Concentrations Authors: Bharti, Lokesh; Jain, Rajmal; Joshi, Chanda; Jaaffrey, S. N. A. Bibcode: 2006IAUJD...3E..37B Altcode: Introduction: The interaction of magnetic fields and plsma flows is one of the fundamental physical processes that leads to many of the dynamic effects observed on the Sun. The present work aims at the correlation of physical quantities such as line of sight magnetic field strength and the bisector velocity at small spatial scales. Methods: We have observed a solar region NOAA 8350 on 1998 October 8 with Universal Birefringent Filter (UBF) in 5576 Å, 6563 Å, 5571 Å continuum and line of sight magnetogram in 6302 Åsimultaneously with G-band images. Bisector velocities were measured for 5576 Å line. Results: Our data analysis reveals that bright points and flux sheets associated to upward and downward motions while micropores and pores associated to upward motions. These flux concentrations shows accelerated motions in deeper layers. Discussion: Upward and downward motions within magnetic flux concentrations is probably due to there dynamic behaviour. Title: Soft and hard X-ray emission from solar flares observed by Solar X-ray Spectrometer (SOXS) mission Authors: Jain, R.; Bharti, L. Bibcode: 2006cosp...36..635J Altcode: 2006cosp.meet..635J Solar X-ray Spectrometer SOXS mission was launched on 08 May 2003 onboard Indian spacecraft to study the energy release and particle acceleration in solar flares in the energy range 4-55 keV To achieve the high spectral resolution Si and CZT detectors were employed We present the temporal and spectral characteristics of soft and hard X-ray emission from 18 M-class flares observed by SOXS mission during 2003 and 2005 We present the line emission characteristics of Fe and Fe Ni features and show the variation of equivalent width and peak energy as a function of temperature which is interpreted as emission contribution of different ionic lines vary with temperature The hard X-ray spectra enabled us to measure the break energy between thermal and non-thermal components as a function of flare duration that allowing determining the contribution of accelerated particles in the flares We also analyzed a few flares associated with CMEs and found that the associated CME is the cause for the flare and not the consequence of the flare Title: Solar X-ray Spectrometer (SOXS) mission: Observations and new results Authors: Jain, R.; Bhatt, N. J.; Bharti, L. Bibcode: 2006ilws.conf...54J Altcode: We present the observations and recently obtained new results from the "Solar X-ray Spectrometer (SOXS)" mission, which was launched onboard GSAT-2 Indian spacecraft on 08 May 2003 by GSLV-D2 rocket to study the solar flares. The state-of-the-art solid state detectors viz. Si PIN and Cadmium-Zinc-Telluride (CZT) were employed that operate at near room temperature (-20 0C). The dynamic energy range of the Si PIN and CZT detectors are 4-25 keV and 4-56 keV, respectively. The Si PIN has sub-keV energy resolution while the CZT has about 1.7 keV energy resolutions throughout the dynamic range. The high sensitivity and sub-keV energy resolution of Si PIN detector allows for measuring the intensity, and equivalent width (w) of the Fe-line and Fe/Ni-line complexes at approximately 6.7 and 8.0 keV as a function of time. We present the results related to the Fe-line complex obtained from the study of 10 M-class flares observed by the SOXS mission. We found that the equivalent width (w) of the Fe-line feature increases exponentially with temperature up to 25 MK but later it increases very slowly up to 35 Mk and then it remains constant up to 45 MK. We compare our measurements of w of the Fe line feature with calculations made earlier by various investigators and propose that these measurements may improve theoretical models. We interpret the variation of w with temperature as the changes in the ionization and recombination conditions in the plasma during the flare interval, and, as a consequence, the contribution from different ionic emission lines also varies. Title: The Solar Flare and CME Induced as a Collision of Two Opposite Polarities on 1997 May 12 Authors: Bharti, L.; Jain, R.; Joshi, C.; Jaaffrey, S. N. A. Bibcode: 2005ASPC..346..327B Altcode: The multispectral observations of active region NOAA 8038 during 10-13 May 1997 are presented. The observations of MDI/SOHO magnetograms show that in this active region continual but discrete growth and decay of magnetic field was taking place indicating either continuous evolution of magnetic flux or emergence of new flux region. The movie of these magnetograms reveal two important results that the major opposite polarities of pre-existing region were approaching towards each other, and a small north polarity flux i.e. moving magnetic feature (MMF) was ejecting out from major north polarity at a quasi-periodicity of about 10 hrs during 10-13 May 1997. It appears that as a result of flux cancellation by one such ejected north polarity flux with a newly emerged south polarity flux around 04:30 UT on 12 May 1997, a moderate but long enduring 1B/C1.3 solar flare. The observation in Hα is presented in detail. Title: MHD Waves Observed in Isolated Brightpoints Authors: Bharti, L.; Jain, R.; Joshi, C.; Jaaffrey, S. N. A. Bibcode: 2005ESASP.600E..79B Altcode: 2005dysu.confE..79B; 2005ESPM...11...79B No abstract at ADS Title: MHD Waves Propogation and Heating of Solar Atmosphere Authors: Bharti, L.; Jain, R.; Joshi, C.; Jaaffrey, S. N. Bibcode: 2005AGUSMSH12A..04B Altcode: We examine oscillations in isolated three bright points co-temporal and co-spatial in photosphere and chromosphere in G-band and Ca II K line. Wavelet analysis was used to study wave packets and identify traveling magnetohydrodynamic waves. In general, it is thought likely that the photosphere and chromosphere oscillates in response to forcing by p-modes and granular buffeting, but they are also influenced strongly by presence of magnetic fields. The observed oscillations reveals evidence for kink-mode waves, traveling up through the chromosphere and coupling with sausage-modes waves. This provides a means for energy depositing in the upper chromosphere. Title: CME and associated phenomena on May 12, 1997 Authors: Bharti, L.; Jain, R.; Joshi, C.; Jaaffrey, S. N. Bibcode: 2005AGUSMSH51C..05B Altcode: The multispectral observations of NOAA active region No. 8038 during 10-13 May 1997 are presented. The observations of MDI/SOHO magnetograms show that in this active region continual but discrete growth and decay of magnetic field was taking place indicating either continuous evolution of magnetic flux or emergence of new flux region. The movie of these magnetograms reveal two important results that the major opposite polarities of pre-existing region were approaching towards each other, and a small north polarity flux i.e. moving magnetic feature (MMF) was ejecting out from major north polarity at a quasi-periodicity of about 10 hrs during 10-13 May 1997. It appears that as a result of flux cancellation by one such ejected north polarity flux with a newly emerged south polarity flux around 04:30 UT on 12 May 1997, a blast wave generated, seen by EIT/SOHO, producing CME and a moderate but long enduring 1B/C1.3 solar flare. The observations in Hα, soft X-ray, hard X-ray, ionospheric absorption, radio and interplanetary scintillations in association to this flare are presented in detail.. The multiwavelength observations of the flare showed occurrence of at least two phases of energy release, first at 04:42 and second at 04:47 UT. We propose a qualitative model to interpret the observations, which, however, also explains the generation of CME and associated flare with two stages of energy release. The occurrence of type II radio burst at 04:54 UT was perhaps due to shock produced by the plasmoid erupted during second energy release at higher altitude in the corona. It appears that the plasmoid traversed through shock in the interplanetary medium so as to enhance the scintillation index on 14 May as inferred from IPS observations. Title: H_α Intensity Oscillations in Solar Flares Authors: Jain, R.; Tripathy, S.; Bharti, L.; Kumar, B. Bibcode: 1999ASPC..183..531J Altcode: 1999hrsp.conf..531J No abstract at ADS Title: High energy photons detection using scintillation counter during total solar eclipse of October 24, 1995. Authors: Jaaffrey, S. N. A.; Jain, R.; Pandya, A.; Bharti, L. Bibcode: 1997KodOB..13..235J Altcode: The authors report the first observations of absorption and enhancement in flux of high energy photons during the total solar eclipse of October 24, 1995. For the purpose of these observations, they employed a scintillation counter to detect high energy radiation in the energy range of 10 keV to 5 MeV. The authors interpret the absorption in the flux below 300 keV due to the passage of the Moon between the Sun and the Earth, while enhancement above 300 keV could have occurred due to the production of secondary radiations from high energy photons.