Low Energy Neutral Atom Signatures of

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Low Energy Neutral Atom Signatures of
Magnetopause Motion in Response to Southward Bz
Michael R. Collier, Thomas E. Moore, Hina Khan,
and Steve Snowden

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XMM X-ray Observations of Solar Wind Charge
Exchange
Sun pulse brightens considerably at time of
solar wind density enhancement. Plan to break
interval up in time and compare NSW observations
with X-ray fluxes.
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Magnetosheath Neutral Atom Emissions
But, sun pulse brightening and sheath emission
only require a magnetopause that is closer to the
Earth - not necessarily higher solar wind ram
pressure. One way to move the magnetopause
closer to the Earth is to erode it with southward
Bz.
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The April 18, 2001 Event
On April 18, 2001, LENA observed sheath
emissions and sun pulse modulation. But between
0100 and 0430, the solar wind ram pressure was
steady.
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Correlation Between LENA Data and Bz
Time-shifted cross-correlation does show a peak
consistent with the solar wind convection
time. Peak correlation not that high
(1) The relationship between Bz and emission is
highly non-linear. (2) Multi-spacecraft studies
show that the IMF does not correlate well even
with itself. (3) The LENA observations are line
of sight and the B-field observations are at a
single point.
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• Sun Pulse/Sheath Brightenings and Radar Data
• Strong correlation between LENA data and
  backscattered radar power from Tiger

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LENA Movie of Sun Pulse Modulation with IMF Bz
Sun pulse brightens in association with more
southward turnings of the IMF while dimming
in response to northward turnings.
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Conclusions

• Have simultaneous observations of solar wind
  charge exchange in X-rays and low energy neutral
  atoms (June 1-2, 2001, day 152-153).
• During the April 18, 2001 (day 108) event,
  neutral solar wind fluxes are modulated by the
  interplanetary magnetic field and interpreted as
  due to magnetopause erosion.
• Signatures associated with reconnection are
  observed at IMAGE and by the Tiger radar at about
  the same time (within a few minutes), which
  supports this association.