Nalin Babulal Trivedi

Cosmic Ray Muon Observation at Southern Space Observatory—SSO (29°S, 53°W)

Under an agreement on scientific cooperation between Brazil and Japan, a prototype detector of cosmic ray muons has been operating since March 2001 at Southern Space Observatory (SSO) located at São Martinho da Serra (29°S, 53°W), Brazil, in order to observe cosmic ray precursors of geomagnetic storms. This detector plays a key roll in the prototype network of muon observations together with two larger detectors operating in Japan and Australia. The planned extension of the detector in its size will complete the global coverage of our muon detector network. The prototype network has already discovered cosmic ray precursors of several magnetic storms, as reported by Munakata et al. (Munakata, K. et al.: 2000, J Geophys Res. 105, A12, pp. 27, 457–27, 468; Munakata K. et al.: 2001, Proceedings of ICRC.) We have also observed the Forbush Decreases (FDs), as well as the precursory enhancements of cosmic ray anisotropy preceding the onsets of geomagnetic storms. This report presents the description of the network and some results obtained since the prototype detector implementation.

X-ray observations in the SAA—Pulsations in electron precipitation accompanied by Pc4 events

Abstract A balloon experiment conducted on December 20, 1994, in the South Atlantic Anomaly (SAA) region, detected events with increases in x-ray flux due to electron precipitation coincident with a mild substorm activity. For the first time in the SAA, the analysis of the x-ray flux associated with the electron precipitation and the geomagnetic H-field component showed simultaneous Pc4 pulsations at periods in the range 95 to 100s. Analysis of a prominent precipitation event of this flight showed direct correlation between the pulsation strength in the x-ray and in the magnetic data and are related to the intensity of the precipitation. While the substorm associated electric fields and currents in the ionosphere can induce amplification of Pc4 pulsations, the x-ray pulsations due to electron precipitation may be related to wave modulated pitch angle scatterings.

Global scale Earth's upper atmosphere monitoring by SACI-1 micro-satellite

Abstract The first Brazilian scientific micro-satellite, SACI-1, is scheduled to be launched in the 2nd semester of 1999. It will be placed in a sun-synchronous polar orbit at a height of 750 km. Four scientific payloads, airglow photometer, high energy particle telescopes, plasma probes and high sensitive magnetometer, are on board to monitor the Earths upper atmosphere environment. The main scientific goal is focused on upper atmospheric dynamics, ionospheric plasma irregularities, anomalous cosmic ray and field-aligned electric current system in the magnetosphere. International collaboration will be necessary, and this will be a key point in order to maximize the utilization of the data.

Analysis of geomagnetic storm variations and count-rate of cosmic ray muons recorded at the Brazilian southern space observatory

An analysis of geomagnetic storm variations and the count rate of cosmic ray muons recorded at the Brazilian Southern Space Observatory - OES/CRS/INPE-MCT, in SMartinho da Serra, RS during the month of November 2004, is presented in this paper. The geomagnetic measurements are done by a three component low noise fluxgate magnetometer and the count rates of cosmic ray muons are recorded by a Muon Scintilator Telescope - MST, both instruments installed at the Observatory. The fluxgate magnetometer measures variations in the three orthogonal components of Earth magnetic field, H (North-South), D (East-West) and Z (Vertical), with data sampling rate of 0.5 Hz. The Muon Scintilator Telescope records hourly count rates. The arrival of a solar disturbance can be identified by observing the decrease in the muon count rate. The goal of this work is to describe the physical morphology and phenomenology observed during the geomagnetic storm of November 2004, using the H component of the geomagnetic field and vertical channel V of the multi-directional muon detector in South of Brazil.