An atmospheric fluorescence detection system has been in operation at Gulmarg (India), during 1972–1978, to search for short-duration (≤ 1 ms) optical pulses produced following the absorption of cosmic X ray and gamma ray photon bursts in the terrestrial atmosphere. A systematic examination of the records reveals no evidence of events with the characteristics of fast atmospheric pulsations (FAP), the millisecond tine scale optical pulses detected during similar studies carried out elsewhere. The complete absence of FAP activity at Gulmarg raises serious doubts about the proposed magnetospheric origin of these events.

Evidence for a nonmagnetospheric origin of fast atmospheric pulsations

Two small air-shower arrays (threshold primary energy approximately 1014 eV) have been operated simultaneously at the mountain stations of Gulmarg and Ootacammund, spaced approximately 2500 km apart. Data collected over 1076 h of overlapping observations have been searched for coincident events on time scales between 1 ms and 1 s and for time-correlated rate enhancements of duration 1, 10 and 60 s. None of these events occurred within +or-15 min of the six cosmic gamma-ray bursts recorded during the corresponding period (1 December 1980 to 28 January 1981) by the Pioneer-Venus mission. The results are discussed in terms of the Grindlay-Fazio model for the emission of relativistic dust grains from pulsars.

A very long baseline search for correlated air showers from relativistic dust grains

A time synchronization system has been developed for the Gulmarg-Srinagar coincidence experiment for detection of primordial black-hole explosions. It utilizes field-markers derived from the synchronization pulse train of Srinagar Television to match the station clocks and give a relative time accuracy of ⪕2 μs. The epoch ambiguity with respect to the absolute time is determined to an accuracy of ⪕1 ms with the help of high frequency time signals from ATA and RWM. The system can presently be employed for the synchronization of remotely-located clocks through the radio time-signals. In future, it can be used for this purpose in the TV synchronization mode also when the national television hook-up becomes possible. The resulting synchronization accuracy of -1 μs should be sufficient for future very-long baseline coincidence experiments in γ-ray and radio astronomies and will dispense with the portable clock method of synchronization which in general, is not readily accessible.

I.K. Kaul

Papers

Time synchronization system in a two-station search for primordial black holes.