  Suzaku detected an enhancement of soft X-ray background associated with solar
eruptions on 2013 April 14-15. The solar eruptions were accompanied by an M6.5
solar flare and a coronal mass ejection with magnetic flux ropes. The enhanced
soft X-ray background showed a slight variation in half a day and then a clear
one in a few hours. The former spectrum was composed of oxygen emission lines,
while the later one was characterized by a series of emission lines from highly
ionized carbon to silicon. The soft X-ray enhancement originated from
geocoronal solar wind charge exchange. However, there appeared to be no
significant time correlation with the solar wind proton flux measured by the
ACE and WIND satellites. From other solar wind signatures, we considered that
an interplanetary shock associated with the coronal mass ejection and a
turbulent sheath immediately behind the shock compressed the ambient solar wind
ions and then resulted in the soft X-ray enhancement. Furthermore, the enriched
emission lines were presumed to be due to an unusual set of ion abundances and
ionization states within the coronal mass ejection. We found a better time
correlation with the solar wind alpha flux rather than the solar wind proton
flux. Our results suggest that the solar wind proton flux is not always a good
indicator of geocoronal solar wind charge exchange, especially associated with
coronal mass ejections. Instead, the solar wind alpha flux should be
investigated when such a soft X-ray enhancement is detected in astronomical
observations.
