NEUTRON MONITOR DATA FOR JUNGFRAUJOCH AND BERN DURING THE GROUND-LEVEL SOLAR COSMIC-RAY EVENT ON 6 NOVEMBER 1997 R. Buetikofer and E.O. Flueckiger Physikalisches Institut, Universitaet Bern Sidlerstrasse 5, CH-3012 Bern, Switzerland This report describes the processing of the data for the ground-level solar cosmic ray event on 6 November 1997 obtained by the following three neutron monitors operated by the Cosmic Ray Group of the University of Bern: i) The standard IGY neutron monitor with 18 BF3- counters at Jungfraujoch (geographic latitude: 46.55 N; geographic longitude 7.98 E; effective vertical cutoff rigidity, Epoch 1990.0: 4.54 GV; altitude 3550 m). This detector is an integral part of the worldwide network of neutron monitors, and data of this monitor have been published regularly since 1958 (Debrunner et al., 1987). ii) The IQSY-NM64 neutron monitor with 3 counter tubes at Jungfraujoch (altitude: 3475 m). This monitor is operating since 1986 (Debrunner et al., 1987; Schubnell, 1988). iii) The special neutron monitor (Buetikofer, 1988) with 58 IGY-type counter tubes in Bern (geographic latitude: 46.95 N; geographic longitude: 7.456 E; altitude: 570 m). The last complete hour (in UT) before the onset of the particle increase at the Earth was used as the baseline time interval, i.e. 6 November 1997, 1100 - 1200 UT. For the Jungfraujoch neutron monitors the following data are given: Hourly data 5 November 1997 0000 - 2400 UT 6 November 1997 0000 - 1100 UT 1-minute data 6 November 1997 1100 - 1800 UT 5-minute data 6 November 1997 1800 - 2400 UT 7 November 1997 0000 - 2400 UT Hourly data 8 November 1997 0000 - 2400 UT For the Bern neutron monitor, the same data are given with the difference that the small-time data include 5- minute values only. All data are presented in the "Standard Format for Cosmic Ray Ground-Level Event Data" as suggested by Shea et al. (1987), and additions according to the document "STANDARD FORMAT FOR COSMIC RAY GROUND-LEVEL ENHANCEMENT DATA" at the GLE data base (downloaded in May 1998). The following names were used to identify the different monitors: JUNGFRAUJ for the 18- IGY and JUNGFRAU2 for the 3-NM64 neutron monitor at Jungfraujoch, BERN for the special neutron monitor in Bern. All counting rates of the neutron monitors were normalized with the same correction factors as used for the publications in the data books and for data sent to the world data centers. The factors for the time interval during the event are given in the following table for the different sections of the neutron monitors. neutron monitor section section section 1 2 3 IGY neutron monitor 0.885 0.894 0.792 Jungfraujoch NM64 neutron monitor 0.955 1.034 1.016 Jungfraujoch special neutron monitor 1.067 1.000 1.060 / Bern 1.000 Section 3 of the IGY neutron monitor at Jungfraujoch is the central section. Section 1 is west of section 3 and section 2 is east of section 3. In the NM64 neutron monitor Jungfraujoch section 1 is located toward the mountain, section 2 is the central section and section 3 is located toward the glacier. For the special neutron monitor in Bern section 1 is AL+AR+BL+BR and section 2 is CL+CR. In contrast to the data books where the count rates of the sections FL and FR are not taken into account, the data in this report include all sections of the special neutron monitor. Section 3 therefore is DL+DR+EL+ER+FL+FR. The correction factor for (DL+DR+EL+ER) is 1.060, whereas for (FL+FR) it is 1.000. (For details see Buetikofer, 1988). In early November 1997 the pressure measurements at Jungfraujoch were disturbed by heavy windstorms. Because of the location of the IGY neutron monitor the barometric measurements at the IGY neutron monitor were affected in particular. Therefore the pressure corrections for both Jungraujoch neutron monitors were based on the pressure data from the NM64 neutron monitor. The respective 1- minute pressure measurements were smoothed by the Savitzky-Golay moving-window averaging method using cubic regression with a moving window of 30 values and one smoothing pass. The size of the moving window was determined by minimizing the scattering of the pressure corrected counting rates. The smoothed pressure values thus obtained were used for pressure corrections of the NM64 neutron monitor. The pressure values for the IGY neutron monitor were determined by subtracting 6.7 mmHg from the smoothed pressure values at the NM64 neutron monitor to adjust for the difference in altitude. (For details see Buetikofer and Flueckiger, 1999) In the special neutron monitor in Bern the counter tubes are placed at different positions relative to the absorbers. Therefore different barometric pressure coefficients were used for the pressure correction of the count rates of the different sections. The barometric pressure coefficients according to Buetikofer (1988) were used. These coefficients are given in the table below. section barometric coefficient in % / mmHg AL, AR -0.975 BL, BR -0.961 CL, CR -0.962 DL, DR -0.920 EL, ER -0.948 FL, FR -0.928 The barometric pressure coefficient of -0.9557 % / mmHg given in line 3 of the header of the standard GLE format for the special neutron monitor in Bern corresponds to an average barometric pressure coefficient for the total count rate. References: Buetikofer, R., Zum Wiederaufbau des Multiplizitaetsneutronenmonitors in Bern, Lizentiatsarbeit, Physikalisches Institut, Universitaet Bern, 1988 Buetikofer, R., E.O. Flueckiger, Pressure Correction of GLE Measurements in Turbulent Winds, 26th ICRC, Salt Lake City, Conference Papers 6, 395, 1999 Debrunner, H., E. Flueckiger, and M. Schubnell, Present and Future Activities of the Bern Cosmic Ray Group in the Field of Solar Neutrons, Workshop on Solar Neutrons, 20th ICRC, Moscow; Special Report of the A.F. Ioffe Physico-Technical Institute of the Academy of Sciences of the USSR, Leningrad, 7, 1987. Schubnell, M., Zum Nachweis solarer Neutronen auf Jungfraujoch, Inauguraldissertation, Physikalisches Institut, Universitaet Bern, 1988 Shea, M.A., D.F. Smart, J.E. Humble, E.O. Flueckiger, L.C. Gentile, and M.R. Nichol, A Revised Standard Format for Cosmic Ray Ground-Level Event Data, 20th ICRC, Moscow, Conference Papers 3, 171, 1987.