Summary

We analyse the precursor of a Forbush decrease (FD) observed with the Global Muon Detector Network on 2006 December 14. An intense geomagnetic storm was also recorded during this FD with the peak Kp index of 8+. By using the two-dimensional map of the cosmic ray intensity produced after removing the contribution from the diurnal anisotropy, we extracted clear signatures of the precursor. A striking feature of this event is that a weak loss-cone (LC) is first recorded more than a day prior to the storm sudden commencement onset (SSC). The long lead time (15.6 hr) of this precursor, which is almost twice the typical value, indicates that the interplanetary magnetic field (IMF) was quieter at this time than typical (less IMF turbulence). We also find an excess intensity from the sunward IMF direction clearly observed 10 hr preceding the SSC onset. This excess intensity is consistent with the measurement of the particles accelerated by the head-on collisions with the approaching s [text ends here].

Authors:Duldig M. Fushishita A. Kuwabara T. Kato C. Yasue S. Bieber J.W. Evenson P. Da Silva M.R. Dal Lago A. Schuch N.J. Tokumaru M. Humble J.E. Sabbah I. Al Jassar H.K. Sharma M.M. Munakata K. Published in: 2010 Category 3: Abstract Program area: Space and Atmospheric Sciences
Duldig M., Fushishita A., Kuwabara T., Kato C., Yasue S., Bieber J.W., Evenson P., Da Silva M.R., Dal Lago A., Schuch N.J., Tokumaru M., Humble J.E., Sabbah I., Al Jassar H.K., Sharma M.M., Munakata K. (2010) Observation of Forbush Decrease Precursors on 2006 December 14 with the Global Muon Detector Network, Astronomical Society of Australia Annual Science Meeting 2010, Hobart, 5-8 July 20;

Related projects

Variations of cosmic radiation [observational] DULDIG, Dr Marcus (Marc) US Coast Guard Icebreaker, Australia (or home country), Mawson
on