1. The Gulmarg Neutron Monitor Ramesh Koul Astrophysical Sciences Division Bhabha Atomic Research Centre Mumbai 400 085

2. NM configurations # IGY 1957/58 eff. ~ 1.9% # NM64 1964 eff. ~ 5.7% # He3 based # Gd doped liquid scintillator

3. Gulmarg Neutron Monitor (GNM) # Originally IGY type - 21xBF3 counters 40mm dia and 900mm length - ~ 0.3 sq.m area # Modified for dual use - Detection of Fusion neutrons from lightning D-D neutrons 2.5MeV - Low energy atmospheric neutron background Solar modulation effects

4. GNM main specifications # Location 36.04N, 74.24E, 2743m asl # High rigidity station (11.6 GV) # Modified IGY type instrument optimized for detection of 2.45 MeV fusion neutrons. # 21 BF3 counters 90cm long, 3.8cm dia # Surface area 30,000 sq.cm. # Top paraffin 8cm thick # Bottom paraffin 28cm thick # Count rate ~36000 per h with an atmospheric pressure coefficient of -0.845% per mbar

5. GNM schematic

6. Counter layout of the GNM

7. Paraffin thickness optimization

8. Pulse amplitude spectrum

9. Oct-Nov 2003 FD event

10. September 2005 FD event

11. Detector profile matching (GNM/ESOIR)

12. Solar wind velocity/GNM count rate (Sept 07-Aug 08)

13. World-wide Network of NM & SNT

14. Proposed multi-station Network of mini GRAPES arrays and Neutron Monitors # Mini arrays (8-16 detectors) at Guwahati, Darjeeling and Gulmarg for ultra-high energy showers. (GRAPES detectors) # NM at Ooty, Darjeeling and Gulmarg for CR and space-weather studies # expand the network in the next phase

15. Summary # The modified lead free Gulmarg Neutron Monitor responds well to solar modulation effects # Possibility of using such NM along with the GRAPES mini-arrays is being investigated.

16. Comparison between IGY and NM64 Neutron Monitors

17. The process begins in space with primary galactic cosmic rays entering the atmosphere after passing through the heliosphere (solar modulation) and geomagnetic field (rigidity cutoff). Most of these primaries are energetic enough to produce a nuclear or high energy interaction initiating a cascade of particles through the atmosphere. As the ensemble of cascades develop the particle density and the particle type distribution varies with atmospheric depth as shown in the Figure. The passage of each particle type through atmosphere is determined by different interaction channels. The dominate interaction depends on particle type, energy and material. The question remains, how does the Neutron Monitor respond to this particles ?? Above energies of 100MeV muons are the dominate species at sea-level, however when considering all energies neutrons dominate in numbers.