Cosmic Ray Laboratory

Raj Bhavan, India

Cosmic Ray Laboratory

Raj Bhavan, India
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Nayak P.K.,Tata Institute of Fundamental Research | Nayak P.K.,Cosmic Ray Laboratory | Gupta S.K.,Tata Institute of Fundamental Research | Gupta S.K.,Cosmic Ray Laboratory | And 6 more authors.
Astroparticle Physics | Year: 2016

A number of groups have reported significant reduction in the flux of low energy (0.1-3 MeV) γ-rays in observations carried out during the past total solar eclipses. However, the contribution of the radon induced radioactivity to the overall γ-ray background can become substantial, especially during episodes of rain. Depending upon the pattern of the rainfall radon induced γ-ray background may vary significantly on time scales of ∼10 min, making the interpretation of the data in terms of an extraterrestrial effect such as a total solar eclipse rather difficult. A reliable estimate of the low energy terrestrial γ-ray (TGR) background is necessary before attempting to measure the possible contribution of any extraterrestrial phenomenon. The knowledge of the precise energies and branching ratios of radon and other radio-isotope induced γ-rays was exploited to accurately reproduce the TGR background, even in the presence of a large and variable contribution from radon induced radioactivity from fresh rain water. The measurement of the TGR background has paved the way for studying the variation of the soft γ-ray flux during the long duration total solar eclipse that occurred on 22 July 2009 in the middle of the Monsoon season in India. © 2015 Elsevier B.V. Allrightsreserved.


Gupta S.K.,Tata Institute of Fundamental Research | Gupta S.K.,Cosmic Ray Laboratory
Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 | Year: 2011

Here, we summarize the papers involving studies of cosmic rays with extensive air showers below 1016eV that were presented during the 32nd International Cosmic Ray Conference (August 11-18, 2011) in Beijing. A total of 55 papers including oral and poster were submitted. However, 47 papers were actually presented in the conference and only these are discussed. For better organization, we have divided the 47 papers into four broad areas namely, the composition studies, anisotropy studies, other related phenomena, techniques and measurements. A total of 12 papers reported studies of the composition of cosmic rays that included several new results. Many exciting results on the anisotropy of multi-TeV cosmic rays were reported possibly for the first time through nine papers. There were ten papers on various other phenomena that included hadronic properties, search for anti-protons and γ-rays, moon shadow studues etc. A total of 16 papers discussed advances made in various techniques and measurements. The breadth and depth of topics covered in most of the papers was very impressive and the future of the field appears to be really exciting.


Arunbabu K.P.,Indian Institute of Science | Antia H.M.,Tata Institute of Fundamental Research | Antia H.M.,Cosmic Ray Laboratory | Dugad S.R.,Tata Institute of Fundamental Research | And 10 more authors.
Astronomy and Astrophysics | Year: 2013

Aims. We seek to identify the primary agents causing Forbush decreases (FDs) in high-rigidity cosmic rays observed from the Earth. In particular, we ask if these FDs are caused mainly by coronal mass ejections (CMEs) from the Sun that are directed towards the Earth, or by their associated shocks. Methods. We used the muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We selected those FD events that have a reasonably clean profile, and can be reasonably well associated with an Earth-directed CME and its associated shock. We employed two models: one that considers the CME as the sole cause of the FD (the CME-only model) and one that considers the shock as the only agent causing the FD (the shock-only model). We used an extensive set of observationally determined parameters for both models. The only free parameter in these models is the level of MHD turbulence in the sheath region, which mediates cosmic ray diffusion (into the CME for the CME-only model, and across the shock sheath for the shock-only model). Results. We find that good fits to the GRAPES-3 multi-rigidity data using the CME-only model require turbulence levels in the CME sheath region that are only slightly higher than those estimated for the quiescent solar wind. On the other hand, reasonable model fits with the shock-only model require turbulence levels in the sheath region that are an order of magnitude higher than those in the quiet solar wind. Conclusions. This observation naturally leads to the conclusion that the Earth-directed CMEs are the primary contributors to FDs observed in high-rigidity cosmic rays. © 2013 ESO.


Gupta S.K.,Tata Institute of Fundamental Research | Gupta S.K.,Cosmic Ray Laboratory
EPJ Web of Conferences | Year: 2013

The GRAPES-3 is a dense extensive air shower array operating with ~400 scintillator detectors and a 560 m2 large tracking muon detector (Eμ > 1 GeV), at Ooty in India. The muon detector has been used to observe acceleration of muons during thunderstorm conditions. The muon multiplicity distribution of the EAS is used to probe the composition of primary cosmic rays below 1 PeV, with an overlap with direct measurements. More recently we have explored the possibility of using the angular distribution of >1 GeV muons to identify the best from among several low- and high-energy hadronic interaction models. We have major expansion plans to enhance the sensitivity of the GRAPES-3 experiment in all of the areas listed above. © Owned by the authors, published by EDP Sciences, 2013.


Kojima H.,Aichi Institute of Technology | Kojima H.,Cosmic Ray Laboratory | Antia H.M.,Cosmic Ray Laboratory | Antia H.M.,Tata Institute of Fundamental Research | And 22 more authors.
Astroparticle Physics | Year: 2015

A radial anisotropy in the flux of cosmic rays in heliosphere was theoretically predicted by Parker and others within the framework of the diffusion-convection mechanism. The solar wind is responsible for sweeping out the galactic cosmic rays, creating a radial density gradient within the heliosphere. This gradient coupled with the interplanetary magnetic field induces a flow of charged particles perpendicular to the ecliptic plane which was measured and correctly explained by Swinson, and is hereafter referred as 'Swinson flow'. The large area GRAPES-3 tracking muon telescope offers a powerful probe to measure the Swinson flow and the underlying radial density gradient of the galactic cosmic rays at a relatively high rigidity of ∼100 GV. The GRAPES-3 data collected over a period of six years (2000-2005) were analyzed and the amplitude of the Swinson flow was estimated to be (0.0644 ± 0.0008)% of cosmic ray flux which was an ∼80σ effect. The phase of the maximum flow was at a sidereal time of (17.70 ± 0.05) h which was 18 min earlier than the expected value of 18 h. This small 18 min phase difference had a significance of ∼6σ indicating the inherent precision of the GRAPES-3 measurement. The radial density gradient of the galactic cosmic rays at a median rigidity of 77 GV was found to be 0.65% AU -1. © 2014 Elsevier B.V. All rights reserved.


News Article | November 8, 2016
Site: www.techtimes.com

The Gamma Ray Astronomy PeV EnergieS 3rd establishment (GRAPES-3) muon telescope, the largest cosmic ray monitor, has observed a burst of galactic cosmic rays suggesting a crack in Earth's magnetic shield. The burst took place when a very large cloud of plasma erupted from the solar corona and collided with our planet, causing a significant compressions of the Earth's magnetosphere. The collision also triggered an acute geomagnetic storm. The telescope is currently located at Tata Institute of Fundamental Research (TIFR)'s Cosmic Ray Laboratory in Ooty, and the galactic cosmic rays it observed were approximately 20 GeV. The event took place on June 22, 2015, and went on for about two hours. The blast happened as the cloud formation of plasma distanced from the solar corona, moving with a speed of roughly 2.5 million kilometers per hour, touched Earth. As a result of this event, a compression of the magnetosphere from 11 to 4 times the radius of our planet was created. The geomagnetic storm created aurora borealis, as well as radio signal interference at the level of various countries around the globe being located in high altitudes. The magnetosphere of our planet is stretched over 600,000 miles, its most important purpose is that it acts as a line of defense, protecting the planet from galactic and solar cosmic rays, along with the lives and environment. The high-intensity radiations contain harmful energetic fields, which could significantly endanger our planet's forms of life. Simulations were carried out by the GRAPES-3 collaboration, in this respect, show that our planet's magnetic shield is cracked for the moment because of the magnetic reconnection and its effects, which permits to the cosmic ray particles of lower energy to enter our atmosphere. The magnetic field of our planet bent the particles roughly 180 degree; therefore, the effects shifted from the day-side to the night zones of Earth. The data observed that night was carefully analyzed and interpreted, through the means of expanded simulations, during the following weeks. The machine was designed in-house by the GRAPES-3 team of engineers and physicists. The place where the instrument was built, just like the telescope, was at the research facility in Ooty. The GRAPE-3 telescope is an Indian-located project consisting of cosmic ray study, through the air shower detector array, as well as large muon detectors. The purpose of this project is to comprehend nuclear composition of the cosmic rays, as well as high-energy gamma-ray astronomy or modulation of solar activity. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


Bhaskar A.,Indian Institute of Geomagnetism | Vichare G.,Indian Institute of Geomagnetism | Arunbabu K.P.,Cosmic Ray Laboratory | Raghav A.,University of Mumbai
Astrophysics and Space Science | Year: 2016

The relationship of Forbush decreases (FDs) observed in Moscow neutron monitor with the interplanetary magnetic field (B) and solar wind speed (Vsw) is investigated in detail for the FDs associated with Interplanetary Coronal Mass Ejections (ICMEs) during 2001–2004. The classical two-step FD events are selected, and characteristics of the first step (mainly associated with shock), as well as of complete decrease (main phase) and recovery phase, are studied here. It is observed that the onset of FD occurs generally after zero to a few hours of shock arrival, indicating in the post-shock region that mainly sheath and ICME act as important drivers of FD. A good correlation is observed between the amplitude of B and associated FD magnitude observed in the neutron count rate of the main phase. The duration of the main phase observed in the neutron count rate also shows good correlation with B. This might indicate that stronger interplanetary disturbances have a large dimension of magnetic field structure which causes longer fall time of FD main phase when they transit across the Earth. It is observed that Vsw and neutron count rate time profiles show considerable similarity with each other during complete FD, especially during the recovery phase of FD. Linear relationship is observed between time duration/e-folding time of FD recovery phase and Vsw. These observations indicate that the FDs are influenced by the inhibited diffusion of cosmic rays due to the enhanced convection associated with the interplanetary disturbances. We infer that the inhibited cross-field diffusion of the cosmic rays due to enhanced B is mainly responsible for the main phase of FD whereas the expansion of ICME contributes in the early recovery phase and the gradual variation of Vsw beyond ICME boundaries contributes to the long duration of FD recovery through reduced convection–diffusion. © 2016, Springer Science+Business Media Dordrecht.


News Article | November 3, 2016
Site: phys.org

The GRAPES-3 muon telescope located at TIFR's Cosmic Ray Laboratory in Ooty recorded a burst of galactic cosmic rays of about 20 GeV, on 22 June 2015 lasting for two hours. The burst occurred when a giant cloud of plasma ejected from the solar corona, and moving with a speed of about 2.5 million kilometers per hour struck our planet, causing a severe compression of Earth's magnetosphere from 11 to 4 times the radius of Earth. It triggered a severe geomagnetic storm that generated aurora borealis, and radio signal blackouts in many high latitude countries. Earth's magnetosphere extends over a radius of a million kilometers, which acts as the first line of defence, shielding us from the continuous flow of solar and galactic cosmic rays, thus protecting life on our planet from these high intensity energetic radiations. Numerical simulations performed by the GRAPES-3 collaboration on this event indicate that the Earth's magnetic shield temporarily cracked due to the occurrence of magnetic reconnection, allowing the lower energy galactic cosmic ray particles to enter our atmosphere. Earth's magnetic field bent these particles about 180 degree, from the day-side to the night-side of the Earth where it was detected as a burst by the GRAPES-3 muon telescope around mid-night on 22 June 2015. The data was analyzed and interpreted through extensive simulation over several weeks by using the 1280-core computing farm that was built in-house by the GRAPES-3 team of physicists and engineers at the Cosmic Ray Laboratory in Ooty. This work has recently been published in Physical Review Letters Solar storms can cause major disruption to human civilization by crippling large electrical power grids, global positioning systems (GPS), satellite operations and communications. The GRAPES-3 muon telescope, the largest and most sensitive cosmic ray monitor operating on Earth is playing a very significant role in the study of such events. This recent finding has generated widespread excitement in the international scientific community, as well as electronic and print media. Explore further: The magnetosphere has a large intake of solar wind energy More information: P. K. Mohanty et al, Transient Weakening of Earth's Magnetic Shield Probed by a Cosmic Ray Burst, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.117.171101


News Article | November 3, 2016
Site: www.eurekalert.org

The GRAPES-3 muon telescope located at TIFR's Cosmic Ray Laboratory in Ooty recorded a burst of galactic cosmic rays of about 20 GeV, on 22 June 2015 lasting for two hours. The burst occurred when a giant cloud of plasma ejected from the solar corona, and moving with a speed of about 2.5 million kilometers per hour struck our planet, causing a severe compression of Earth's magnetosphere from 11 to 4 times the radius of Earth. It triggered a severe geomagnetic storm that generated aurora borealis, and radio signal blackouts in many high latitude countries. Earth's magnetosphere extends over a radius of a million kilometers, which acts as the first line of defence, shielding us from the continuous flow of solar and galactic cosmic rays, thus protecting life on our planet from these high intensity energetic radiations. Numerical simulations performed by the GRAPES-3 collaboration on this event indicate that the Earth's magnetic shield temporarily cracked due to the occurrence of magnetic reconnection, allowing the lower energy galactic cosmic ray particles to enter our atmosphere. Earth's magnetic field bent these particles about 180 degree, from the day-side to the night-side of the Earth where it was detected as a burst by the GRAPES-3 muon telescope around mid-night on 22 June 2015. The data was analyzed and interpreted through extensive simulation over several weeks by using the 1280-core computing farm that was built in-house by the GRAPES-3 team of physicists and engineers at the Cosmic Ray Laboratory in Ooty. This work has recently been published in Physical Review Letters Solar storms can cause major disruption to human civilization by crippling large electrical power grids, global positioning systems (GPS), satellite operations and communications. The GRAPES-3 muon telescope, the largest and most sensitive cosmic ray monitor operating on Earth is playing a very significant role in the study of such events. This recent finding has generated widespread excitement in the international scientific community, as well as electronic and print media.


News Article | November 3, 2016
Site: www.sciencedaily.com

The GRAPES-3 muon telescope located at TIFR's Cosmic Ray Laboratory in Ooty recorded a burst of galactic cosmic rays of about 20 GeV, on 22 June 2015 lasting for two hours. The burst occurred when a giant cloud of plasma ejected from the solar corona, and moving with a speed of about 2.5 million kilometers per hour struck our planet, causing a severe compression of Earth's magnetosphere from 11 to 4 times the radius of Earth. It triggered a severe geomagnetic storm that generated aurora borealis, and radio signal blackouts in many high latitude countries. Earth's magnetosphere extends over a radius of a million kilometers, which acts as the first line of defence, shielding us from the continuous flow of solar and galactic cosmic rays, thus protecting life on our planet from these high intensity energetic radiations. Numerical simulations performed by the GRAPES-3 collaboration on this event indicate that the Earth's magnetic shield temporarily cracked due to the occurrence of magnetic reconnection, allowing the lower energy galactic cosmic ray particles to enter our atmosphere. Earth's magnetic field bent these particles about 180 degree, from the day-side to the night-side of the Earth where it was detected as a burst by the GRAPES-3 muon telescope around mid-night on 22 June 2015. The data was analyzed and interpreted through extensive simulation over several weeks by using the 1280-core computing farm that was built in-house by the GRAPES-3 team of physicists and engineers at the Cosmic Ray Laboratory in Ooty. This work has recently been published in Physical Review Letters. Solar storms can cause major disruption to human civilization by crippling large electrical power grids, global positioning systems (GPS), satellite operations and communications. The GRAPES-3 muon telescope, the largest and most sensitive cosmic ray monitor operating on Earth is playing a very significant role in the study of such events. This recent finding has generated widespread excitement in the international scientific community, as well as electronic and print media.

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