EastWest Effect seen in the BFEM data

1
East-West Effect seen in the BFEM data

• Tsunefumi Mizuno
• May 29, 2002

2
Calibration of the magnetometer
A magnetometer was mounted on the gondola and
calibrated by Gary Godfrey and Bob Schaefer
magnetometer is mounted along y-axis
Azimuth angle in pitch-roll plot is the same with
that between y-axis and west (red).
3
Time history of pitch/roll voltage(1)
As already showed by Dave Lauben, roll/pitch
voltage (direction of BFEM) of Run54 was
unstable. We will not use this data.
Center (2.8, 2.66)
The direction of BFEM in Run55 was rather stable.
4
Time history of pitch/roll voltage(2)
Pitch voltage of Run55
Roll voltage of Run55
The direction of the BFEM was stable in the
latter half of the run.
5
East-West Effect seen in the BFEM data
In the latter half of Run55, the direction of the
BFEM was stable. We separated the data into two.
Run55
former half
latter half

• We utilized reconstruction program and select
  single/straight track events.
• We calculated azimuth angle assuming that
  particle goes downward.
• Then, the flux of particles coming from east is
  lowest -gt east-west effect.

particle comes from east
6
Summary

• The direction of the BFEM was measured by
  magnetometer mounted on the gondola.
• The direction of the BFEM was unstable in Run54
  (during ascent), but rather stable in Run55
  (level flight).
• Azimuth angle distribution of particles (single
  and straight track) shows asymmetry, and can be
  explained by east-west effect.