Polar observations of the characteristics of the dayside high altitude cusp

T. A. FRITZ, J. CHEN, J. NIEHOFCenter for Space Physics at Boston University

Polar PI conference callDecember 3, 2004

The Chapman Ferraro Cusp

Observationally Polar has shown that the cusp is a large region and is the site of continuous large fluxes of energetic particles.

At BU we feel that we have established that these energetic particles are produced there and we are searching for the mechanism that does that.

10

10

Cusp Energy Density comparison published by Chang et al., 1998

June 20, 1996

8/27/96

Total Pressure (x10)

Magnetic Pressure

Plasma Prep. Pressure

8/27/96 9/18/96

4/20/99 4/24/99

8/27/96

Btotal

Vx

MICS He++

MICS O+6

MICS H+

Hydra ions

Btotal

P prep (electrons)

P prep (ions)

Ion Density (Hydra)

Ion Density (Tide)

EFI Density

8/27/96

Btotal

Vx (km/s)

MICS He++

MICS O+6

MICS H+

Hydra ions

9/18/96

Btotal

P prep (electrons)

P prep (ions)

Ion Density (Hydra)

Ion Density (Tide)

EFI Density

Btotal

Vx (km/s)

MICS He++

MICS O+6

MICS H+

Hydra ions

4/20/99

Btotal

P prep (electrons)

P prep (ions)

Ion Density (Hydra)

Ion Density (Tide)

EFI Density

Btotal

Vx (km/s)

MICS He++

MICS O+6

MICS H+

Hydra ions

4/24/99

Btotal

P prep (electrons)

P prep (ions)

Ion Density (Hydra)

Ion Density (Tide)

EFI Density

Ions Electrons

9/18/96

R=-0.86 R=-0.87

R=-0.93 R=-0.95

Ions Electons

8/27/99

R=-0.90 R=-0.95

R=-0.83 R=-0.91

Conclusions:

We have attempted to understand the components that must provide the energy density within the high-altitude cusp.

With the advertised data from the Polar team there is a deficiency of the measured plasma pressure in creating a balance.

The local plasma from the solar wind creates the diamagnetic cavity.

The perpendicular pressure provided by both the ions and electrons are highly anti-correlated with the turbulence as expected but the electrons surprisingly show a higher level of anti-correlation.

The sense of the polarization of the observed electric component of the turbulence in the direction perpendicular to B can provide resonate acceleration of ions rapidly to high energies.