Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: How are Forbush decreases related to interplanetary magnetic field
  enhancements ?   Aims. Forbush decrease (FD) is a transient decrease followed by a gradual
recovery in the observed galactic cosmic ray intensity. We seek to understand
the relationship between the FDs and near-Earth interplanetary magnetic field
(IMF) enhancements associated with solar coronal mass ejections (CMEs).
Methods. We use muon data at cutoff rigidities ranging from 14 to 24 GV from
the GRAPES-3 tracking muon telescope to identify FD events. We select those FD
events that have a reasonably clean profile, and magnitude > 0.25%. We use IMF
data from ACE/WIND spacecrafts. We look for correlations between the FD profile
and that of the one hour averaged IMF. We ask if the diffusion of high energy
protons into the large scale magnetic field is the cause of the lag observed
between the FD and the IMF. Results. The enhancement of the IMF associated with
FDs occurs mainly in the shock-sheath region, and the turbulence level in the
magnetic field is also enhanced in this region. The observed FD profiles look
remarkably similar to the IMF enhancement profiles. The FDs typically lag the
IMF enhancement by a few hours. The lag corresponds to the time taken by high
energy protons to diffuse into the magnetic field enhancement via cross-field
diffusion. Conclusions. Our findings show that high rigidity FDs associated
with CMEs are caused primarily by the cumulative diffusion of protons across
the magnetic field enhancement in the turbulent sheath region between the shock
and the CME.

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The categories of this paper are: eess
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph