Polar Scientists Find Unexpected Energetic Ions in the Earth

1
Polar Scientists Find Unexpected Energetic Ions
in the Earths Magnetic Cusp
The cusp is traditionally associated with
particles of solar wind origin ions
80 eV - 5 keV electrons 20 eV - 1 keV Polar
often observes highly energetic ions in the
cusp 10 keV up to several MeV These are more
typical of the trapped ring current and radiation
belt populations!
A new source for energetic ions within the
magnetosphere?
Fritz, T. A., J. Chen, R. B. Sheldon, H. E.
Spence, J. F. Fennell, S. Livi, C. T. Russell,
and J. S. Pickett, Cusp energetic particle
events measured by POLAR spacecraft, Phys. and
Chem. of the Earth, 24, 135, 1999.
2
Particles on field lines in the cusp have access
to basically all of geospace
Polar Scientists Find Unexpected Energetic Ions
in the Earth's Magnetic Cusp
The Earth's cusps are singular regions in the
magnetosphere at which all field lines threading
the cavity boundary (magnetopause) come together.
The cusp has two important features 1. It is
the only place the solar wind has direct access
to low altitudes. 2. Through convection, it is
the only place in the magnetosphere that is
virtually connected to everywhere.
3
Measurements
Polar Scientists Find Unexpected Energetic Ions
in the Earth's Magnetic Cusp
POLAR carries the full range of particle
instrumentation to resolve details of the
complete spectrum of cusp energetic ions HYDRA
total ion distributions from
10 eV to 20 keV TIMAS
plasma ion composition from
15eV/Q to 32 keV/Q CAMMICE
energetic ion composition from
1 keV/Q to 60 MeV/Q. CEPPAD IPS
total ion distribution from
30 keV to 1 MeV The full energy range from
thermal solar wind to MeV energies is present in
the cusp and the detailed spectrum is used to
unravel possible sources for these ions.
4
A significant portion of the particle spectrum is
consistent with solar wind accelerated through
the quasi-parallel bow shock.
Polar Scientists Find Unexpected Energetic Ions
in the Earth's Magnetic Cusp
Karlheinz Trattner of Lockheed finds that the
spectrum up to 10keV is consistent with direct
access of shocked solar wind. The range from 10
- 150 keV fits the bow shock accelerated
ions. Connectivity from the bow shock to cusp has
never before been so directly implicated.
This may establish a new connection process
between the solar wind and the magnetosphere.
The origin of the high energy tail is still a
topic of considerable scientific debate.
5
Conclusion/Implications
Polar Scientists Find Unexpected Energetic Ions
in the Earth's Magnetic Cusp
The highest-energy portion of the spectrum may
originate through acceleration mechanisms local
to the cusp
Ted Fritz and Jiasheng Chen of Boston University
have suggested that acceleration mechanisms local
to the cusp act to create the energetic particle
spectrum within the cusp and have identified
intense magnetic fluctuations as the power
source.
Discovery of new energetic ion population in the
cusp a significant portion of which originates
through a direct connection to the bow
shock. Origin of highest energy portion of
spectrum remains under dispute the evolving
Polar orbit offers the best opportunity for
resolution. Given the cusps connectivity, the
presence of these Cusp Energetic Particles (CEP)
has major implications for theories regarding
energetic particle populations within the
magnetosphere the radiation belts and ring
current dramatically altering current
perceptions of the sources and dynamics of these
regions.