Tanmoy Samanta - Academia.edu (original) (raw)
Papers by Tanmoy Samanta
International journal of statistics and applications, 2020
Are chemical fertilizers associated with the increased yield rate of the principal crop in West B... more Are chemical fertilizers associated with the increased yield rate of the principal crop in West Bengal? Using data of 18 districts of West Bengal for the period 2000-01 to 2011-12 this paper examines whether the marginal and partial (or better orthopartial, 2008) explanatory power of chemical fertilizers in explaining the yield rate of the principal crop in West Bengal is significant or not. By considering different types of chemical fertilizers it is observed that nitrogen, phosphate, potash, and total chemical fertilizer are both marginally and partially significant for increasing the yield rate of the principal crop in West Bengal.
The identification of solar coronal holes (CHs) observed in Extreme Ultraviolet (EUV) intensity i... more The identification of solar coronal holes (CHs) observed in Extreme Ultraviolet (EUV) intensity images of the Sun is key in improving our understanding of their association with solar magnetic fields and heliophysics. In particular, CHs at the poles of the Sun are a notorious source of fast solar wind and thus warrant further study, most notably in the context of space-weather forecasting. This has consequently led to the development of various segmentation methods for their identification, including supervised machine learning. We introduce the SEARCH project to combine EUV data from the three vantage points offered by the SoHO, STEREO-A and STEREO-B satellites during the 2010-2014 epoch to produce synchronic maps and apply unsupervised learning methods including clustering and convolutional neural networks for the segmentation of CHs. SEARCH segmentation maps provide a venue to explore the relationship between CH pole areas, geomagnetic activity, and the magnetic activity cycle (d...
The million-degree hot solar corona maintains its high temperature and compensates for its radiat... more The million-degree hot solar corona maintains its high temperature and compensates for its radiative losses by continuously acquiring an energy flux of approx\approxapprox10$^{3}$ W m$^{-2,}$. Recent studies suggest that energy transport in the solar corona is associated with localized magnetic flux-tubes, which can channel various kinds of magnetohydrodynamic (MHD) waves and shocks as heating candidates. Dissipation of electric current via magnetic reconnection provides an alternate mechanism to heat the solar corona. However, there are various physical conditions that need to be established appropriately in the reconnection region to generate its high rate and subsequent energy release. Using multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), we present a novel physical scenario for the formation of a temporary X-point in the solar corona, where plasma dynamics is forced externally by a moving prominence. Natural di...
Science China Technological Sciences, 2020
Journal of Food Processing and Preservation, 2021
Journal of Physics: Conference Series, 2020
Many solar coronal jets result from erupting miniature-filament (“minifilament”) magnetic flux ro... more Many solar coronal jets result from erupting miniature-filament (“minifilament”) magnetic flux ropes that reconnect with encountered surrounding far-reaching field. Many of those minifilament flux ropes are apparently built and triggered to erupt by magnetic flux cancelation. If that cancelation (or some other process) results in the flux rope’s field having twist, then the reconnection with the far-reaching field transfers much of that twist to that reconnected far-reaching field. In cases where that surrounding field is open, the twist can propagate to far distances from the Sun as a magnetic-twist Alfvénic pulse. We argue that such pulses from jets could be the kinked-magnetic-field structures known as “switchbacks,” detected in the solar wind during perihelion passages of the Parker Solar Probe (PSP). For typical coronal-jet-generated Alfvénic pulses, we expect that the switchbacks would flow pastPSPwith a duration of several tens of minutes; larger coronal jets might produce sw...
The Astrophysical Journal, 2018
The barbs or legs of some prominences show an apparent motion of rotation, which are often termed... more The barbs or legs of some prominences show an apparent motion of rotation, which are often termed solar tornadoes. It is under debate whether the apparent motion is a real rotating motion, or caused by oscillations or counter-streaming flows. We present analysis results from spectroscopic observations of two tornadoes by the Interface Region Imaging Spectrograph. Each tornado was observed for more than 2.5 hours. Doppler velocities are derived through a single Gaussian fit to the Mg ii k 2796Å and Si iv 1393Å line profiles. We find coherent and stable redshifts and blueshifts adjacent to each other across the tornado axes, which appears to favor the interpretation of these tornadoes as rotating cool plasmas with temperatures of 10 4 K-10 5 K. This interpretation is further supported by simultaneous observations of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, which reveal periodic motions of dark structures in the tornadoes. Our results demonstrate that spectroscopic observations can provide key information to disentangle different physical processes in solar prominences.
The Astrophysical Journal, 2020
We examine Big Bear Solar Observatory (BBSO) Goode Solar Telescope (GST) high spatial resolution ... more We examine Big Bear Solar Observatory (BBSO) Goode Solar Telescope (GST) high spatial resolution (0 06), high-cadence (3.45 s), Hα-0.8 Å images of central-disk solar spicules, using data of Samanta et al. We compare with coronal-jet chromospheric-component observations of Sterling et al. Morphologically, bursts of spicules, referred to as "enhanced spicular activities" by Samanta et al., appear as scaled-down versions of the jet's chromospheric component. Both the jet and the enhanced spicular activities appear as chromospheric-material strands, undergoing twisting-type motions of ∼20-50 kms −1 in the jet and ∼20-30 kms −1 in the enhanced spicular activities. Presumably, the jet resulted from a minifilament-carrying magnetic eruption. For two enhanced spicular activities that we examine in detail, we find tentative candidates for corresponding erupting microfilaments, but not the expected corresponding base brightenings. Nonetheless, the enhanced-spicularactivities' interacting mixed-polarity base fields, frequent-apparent-twisting motions, and morphological similarities to the coronal jet's chromospheric-temperature component, suggest that erupting microfilaments might drive the enhanced spicular activities but be hard to detect, perhaps due to Hα opacity. Degrading the BBSO/GST-image resolution with a 1 0-FWHM smoothing function yields enhanced spicular activities resembling the "classical spicules" described by, e.g., Beckers. Thus, a microfilament eruption might be the fundamental driver of many spicules, just as a minifilament eruption is the fundamental driver of many coronal jets. Similarly, a 0 5-FWHM smoothing renders some enhanced spicular activities to resemble previously reported "twinned" spicules, while the full-resolution features might account for spicules sometimes appearing as 2D-sheetlike structures.
Journal of Food Processing and Preservation, 2019
Tea is made from young shoots of the plant Camellia sinensis. Processing steps in black tea manuf... more Tea is made from young shoots of the plant Camellia sinensis. Processing steps in black tea manufacturing are withering, maceration, fermentation (oxidation), and drying. Generally, two leaves and a bud are used for processing of tea. Total polyphenol content in green tea shoots is 25%-30% of dry solids (Tanaka, Tsai, & Wang, 2009). Fresh leaves are withered for 14-16 hr where leaves are conditioned physically, as well as chemically for subsequent processing stages. Withered leaves are macerated either by orthodox or CTC (crush-tear-curl) method to express juice from the cell sap. In orthodox manufacturing, leaves are rolled under pressure and part of the juice from cell sap is expressed, whereas leaves are fully smashed and granulated in CTC maceration. The polyphenols and enzymes, which are present in different compartments in leaves, are mixed. This initiates a series of enzyme-catalyzed oxidative reactions. Polyphenols present in leaves are oxidized to produce polymerized pigment compounds like theaflavins (TF) and thearubigins (TR). (Tanaka et al., 2009). Depending of the extent of maceration, oxidation duration ranges from 45 min to 3 hr. Major tea leaf polyphenols are catechins, which include (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate (EGCG) (Tanaka et al., 2009). Catechins are responsible for characteristic bitter and astringent
Science China Technological Sciences, 2019
Solar ultraviolet (UV) bursts are small-scale compact brightenings in transition region images. T... more Solar ultraviolet (UV) bursts are small-scale compact brightenings in transition region images. The spectral profiles of transition region lines in these bursts are significantly enhanced and broadened, often with chromospheric absorption lines such as Ni ii 1335.203 and 1393.330 Å superimposed. We investigate the properties of several UV bursts using a coordinated observation of the Interface Region Imaging Spectrograph (IRIS), Solar Dynamics Observatory (SDO), and Hinode on 2015 February 7. We have identified 12 UV bursts, and 11 of them reveal small blueshifts of the Ni ii absorption lines. However, the Ni ii lines in one UV burst exhibit obvious redshifts of ∼20 km s −1 , which appear to be related to the cold plasma downflows observed in the IRIS slit-jaw images. We also examine the three-dimensional magnetic field topology using a magnetohydrostatic model, and find that some UV bursts are associated with magnetic null points or bald patches. In addition, we find that these UV bursts reveal no obvious coronal signatures from the observations of the Atmospheric Imaging Assembly (AIA) on board SDO and the EUV Imaging Spectrometer (EIS) on board Hinode.
Physical Review Letters, 2019
The Astrophysical Journal, 2018
The Astrophysical Journal, 2019
Ellerman bombs (EBs) are small-scale intense brightenings in Hα wing images, which are generally ... more Ellerman bombs (EBs) are small-scale intense brightenings in Hα wing images, which are generally believed to be signatures of magnetic reconnection around the temperature minimum region of the solar atmosphere. They have a flame-like morphology when observed near the solar limb. Recent observations from the Interface Region Imaging Spectrograph (IRIS) reveal another type of small-scale reconnection events, termed UV bursts, in the lower solar atmosphere. Though previous observations have shown a clear coincidence of some UV bursts and EBs, the exact relationship between these two phenomena is still under debate. We investigate the spatial and temporal relationship between flame-like EBs and UV bursts using joint near-limb observations between the 1.6-meter Goode Solar Telescope (GST) and IRIS. In total 161 EBs have been identified from the GST observations, and ∼20 of them reveal signatures of UV bursts in the IRIS images. Interestingly, we find that these UV bursts have a tendency to appear at the upper parts of their associated flame-like EBs. The intensity variations of most EB-related UV bursts and their corresponding EBs match well. Our results suggest that some of these UV bursts and EBs are likely formed at different heights during a common reconnection process.
The Astrophysical Journal, 2019
Earth and Planetary Physics, 2017
International journal of statistics and applications, 2020
Are chemical fertilizers associated with the increased yield rate of the principal crop in West B... more Are chemical fertilizers associated with the increased yield rate of the principal crop in West Bengal? Using data of 18 districts of West Bengal for the period 2000-01 to 2011-12 this paper examines whether the marginal and partial (or better orthopartial, 2008) explanatory power of chemical fertilizers in explaining the yield rate of the principal crop in West Bengal is significant or not. By considering different types of chemical fertilizers it is observed that nitrogen, phosphate, potash, and total chemical fertilizer are both marginally and partially significant for increasing the yield rate of the principal crop in West Bengal.
The identification of solar coronal holes (CHs) observed in Extreme Ultraviolet (EUV) intensity i... more The identification of solar coronal holes (CHs) observed in Extreme Ultraviolet (EUV) intensity images of the Sun is key in improving our understanding of their association with solar magnetic fields and heliophysics. In particular, CHs at the poles of the Sun are a notorious source of fast solar wind and thus warrant further study, most notably in the context of space-weather forecasting. This has consequently led to the development of various segmentation methods for their identification, including supervised machine learning. We introduce the SEARCH project to combine EUV data from the three vantage points offered by the SoHO, STEREO-A and STEREO-B satellites during the 2010-2014 epoch to produce synchronic maps and apply unsupervised learning methods including clustering and convolutional neural networks for the segmentation of CHs. SEARCH segmentation maps provide a venue to explore the relationship between CH pole areas, geomagnetic activity, and the magnetic activity cycle (d...
The million-degree hot solar corona maintains its high temperature and compensates for its radiat... more The million-degree hot solar corona maintains its high temperature and compensates for its radiative losses by continuously acquiring an energy flux of approx\approxapprox10$^{3}$ W m$^{-2,}$. Recent studies suggest that energy transport in the solar corona is associated with localized magnetic flux-tubes, which can channel various kinds of magnetohydrodynamic (MHD) waves and shocks as heating candidates. Dissipation of electric current via magnetic reconnection provides an alternate mechanism to heat the solar corona. However, there are various physical conditions that need to be established appropriately in the reconnection region to generate its high rate and subsequent energy release. Using multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), we present a novel physical scenario for the formation of a temporary X-point in the solar corona, where plasma dynamics is forced externally by a moving prominence. Natural di...
Science China Technological Sciences, 2020
Journal of Food Processing and Preservation, 2021
Journal of Physics: Conference Series, 2020
Many solar coronal jets result from erupting miniature-filament (“minifilament”) magnetic flux ro... more Many solar coronal jets result from erupting miniature-filament (“minifilament”) magnetic flux ropes that reconnect with encountered surrounding far-reaching field. Many of those minifilament flux ropes are apparently built and triggered to erupt by magnetic flux cancelation. If that cancelation (or some other process) results in the flux rope’s field having twist, then the reconnection with the far-reaching field transfers much of that twist to that reconnected far-reaching field. In cases where that surrounding field is open, the twist can propagate to far distances from the Sun as a magnetic-twist Alfvénic pulse. We argue that such pulses from jets could be the kinked-magnetic-field structures known as “switchbacks,” detected in the solar wind during perihelion passages of the Parker Solar Probe (PSP). For typical coronal-jet-generated Alfvénic pulses, we expect that the switchbacks would flow pastPSPwith a duration of several tens of minutes; larger coronal jets might produce sw...
The Astrophysical Journal, 2018
The barbs or legs of some prominences show an apparent motion of rotation, which are often termed... more The barbs or legs of some prominences show an apparent motion of rotation, which are often termed solar tornadoes. It is under debate whether the apparent motion is a real rotating motion, or caused by oscillations or counter-streaming flows. We present analysis results from spectroscopic observations of two tornadoes by the Interface Region Imaging Spectrograph. Each tornado was observed for more than 2.5 hours. Doppler velocities are derived through a single Gaussian fit to the Mg ii k 2796Å and Si iv 1393Å line profiles. We find coherent and stable redshifts and blueshifts adjacent to each other across the tornado axes, which appears to favor the interpretation of these tornadoes as rotating cool plasmas with temperatures of 10 4 K-10 5 K. This interpretation is further supported by simultaneous observations of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, which reveal periodic motions of dark structures in the tornadoes. Our results demonstrate that spectroscopic observations can provide key information to disentangle different physical processes in solar prominences.
The Astrophysical Journal, 2020
We examine Big Bear Solar Observatory (BBSO) Goode Solar Telescope (GST) high spatial resolution ... more We examine Big Bear Solar Observatory (BBSO) Goode Solar Telescope (GST) high spatial resolution (0 06), high-cadence (3.45 s), Hα-0.8 Å images of central-disk solar spicules, using data of Samanta et al. We compare with coronal-jet chromospheric-component observations of Sterling et al. Morphologically, bursts of spicules, referred to as "enhanced spicular activities" by Samanta et al., appear as scaled-down versions of the jet's chromospheric component. Both the jet and the enhanced spicular activities appear as chromospheric-material strands, undergoing twisting-type motions of ∼20-50 kms −1 in the jet and ∼20-30 kms −1 in the enhanced spicular activities. Presumably, the jet resulted from a minifilament-carrying magnetic eruption. For two enhanced spicular activities that we examine in detail, we find tentative candidates for corresponding erupting microfilaments, but not the expected corresponding base brightenings. Nonetheless, the enhanced-spicularactivities' interacting mixed-polarity base fields, frequent-apparent-twisting motions, and morphological similarities to the coronal jet's chromospheric-temperature component, suggest that erupting microfilaments might drive the enhanced spicular activities but be hard to detect, perhaps due to Hα opacity. Degrading the BBSO/GST-image resolution with a 1 0-FWHM smoothing function yields enhanced spicular activities resembling the "classical spicules" described by, e.g., Beckers. Thus, a microfilament eruption might be the fundamental driver of many spicules, just as a minifilament eruption is the fundamental driver of many coronal jets. Similarly, a 0 5-FWHM smoothing renders some enhanced spicular activities to resemble previously reported "twinned" spicules, while the full-resolution features might account for spicules sometimes appearing as 2D-sheetlike structures.
Journal of Food Processing and Preservation, 2019
Tea is made from young shoots of the plant Camellia sinensis. Processing steps in black tea manuf... more Tea is made from young shoots of the plant Camellia sinensis. Processing steps in black tea manufacturing are withering, maceration, fermentation (oxidation), and drying. Generally, two leaves and a bud are used for processing of tea. Total polyphenol content in green tea shoots is 25%-30% of dry solids (Tanaka, Tsai, & Wang, 2009). Fresh leaves are withered for 14-16 hr where leaves are conditioned physically, as well as chemically for subsequent processing stages. Withered leaves are macerated either by orthodox or CTC (crush-tear-curl) method to express juice from the cell sap. In orthodox manufacturing, leaves are rolled under pressure and part of the juice from cell sap is expressed, whereas leaves are fully smashed and granulated in CTC maceration. The polyphenols and enzymes, which are present in different compartments in leaves, are mixed. This initiates a series of enzyme-catalyzed oxidative reactions. Polyphenols present in leaves are oxidized to produce polymerized pigment compounds like theaflavins (TF) and thearubigins (TR). (Tanaka et al., 2009). Depending of the extent of maceration, oxidation duration ranges from 45 min to 3 hr. Major tea leaf polyphenols are catechins, which include (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC), and (-) epigallocatechin gallate (EGCG) (Tanaka et al., 2009). Catechins are responsible for characteristic bitter and astringent
Science China Technological Sciences, 2019
Solar ultraviolet (UV) bursts are small-scale compact brightenings in transition region images. T... more Solar ultraviolet (UV) bursts are small-scale compact brightenings in transition region images. The spectral profiles of transition region lines in these bursts are significantly enhanced and broadened, often with chromospheric absorption lines such as Ni ii 1335.203 and 1393.330 Å superimposed. We investigate the properties of several UV bursts using a coordinated observation of the Interface Region Imaging Spectrograph (IRIS), Solar Dynamics Observatory (SDO), and Hinode on 2015 February 7. We have identified 12 UV bursts, and 11 of them reveal small blueshifts of the Ni ii absorption lines. However, the Ni ii lines in one UV burst exhibit obvious redshifts of ∼20 km s −1 , which appear to be related to the cold plasma downflows observed in the IRIS slit-jaw images. We also examine the three-dimensional magnetic field topology using a magnetohydrostatic model, and find that some UV bursts are associated with magnetic null points or bald patches. In addition, we find that these UV bursts reveal no obvious coronal signatures from the observations of the Atmospheric Imaging Assembly (AIA) on board SDO and the EUV Imaging Spectrometer (EIS) on board Hinode.
Physical Review Letters, 2019
The Astrophysical Journal, 2018
The Astrophysical Journal, 2019
Ellerman bombs (EBs) are small-scale intense brightenings in Hα wing images, which are generally ... more Ellerman bombs (EBs) are small-scale intense brightenings in Hα wing images, which are generally believed to be signatures of magnetic reconnection around the temperature minimum region of the solar atmosphere. They have a flame-like morphology when observed near the solar limb. Recent observations from the Interface Region Imaging Spectrograph (IRIS) reveal another type of small-scale reconnection events, termed UV bursts, in the lower solar atmosphere. Though previous observations have shown a clear coincidence of some UV bursts and EBs, the exact relationship between these two phenomena is still under debate. We investigate the spatial and temporal relationship between flame-like EBs and UV bursts using joint near-limb observations between the 1.6-meter Goode Solar Telescope (GST) and IRIS. In total 161 EBs have been identified from the GST observations, and ∼20 of them reveal signatures of UV bursts in the IRIS images. Interestingly, we find that these UV bursts have a tendency to appear at the upper parts of their associated flame-like EBs. The intensity variations of most EB-related UV bursts and their corresponding EBs match well. Our results suggest that some of these UV bursts and EBs are likely formed at different heights during a common reconnection process.
The Astrophysical Journal, 2019
Earth and Planetary Physics, 2017