Polar scientists find unexpected energetic ions in the earth s magnetic cusp
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Polar Scientists Find Unexpected Energetic Ions in the Earth’s 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

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Polar scientists find unexpected energetic ions in the earth s magnetic cusp l.jpg
Polar Scientists Find Unexpected Energetic Ions in the Earth’s 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.


Particles on field lines in the cusp have access to basically all of geospace l.jpg
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.


Measurements l.jpg
Measurements: basically all of geospace

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.


Slide4 l.jpg
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.


Conclusion implications l.jpg
Conclusion/Implications: with solar wind accelerated through the quasi-parallel bow shock.

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 cusp’s 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.


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