Earth's Quasi-steady Magnetopause Interfaces and Boundary Layers

Name Description Spatial scale
(Thickness x Width, Re)
Time scale (hrs) Spacecraft/
Scientists who defined/
agreed with
Depletion layer A magnetosheath region just outside the magnetopause which plasma density decreases but magnetic field strength increases relative to the adjacent magnetosheath plasma. It mostly occurs when the IMF is northward 1x10 10 ISEE/FPE, AMPTE/IRM plasma ?, D. Fairfield, D. Sibeck, P. Song
Slow mode transition layer A magnetosheath region just outside the magnetopause which plasma density and magnetic field strength changes in a manner similar to the slow mode MHD waves. That is the variations in density and field strength is out-of-phase. This often occurs when the IMF is northward. 1x10 10 ISEE/FPE P. Song
Magnetic field line merging layer A region just inside the magnetopause where magnetic field merging process occurs. 0.1x10 10 ISEE/FPE ?,Petcheck, B. Sonnerup
Magnetopause An interface separates magnetospheric plasma and solar wind plasma. It is located at where the plasma density, plasma temperature, and magnetic field change dramatically from one plasma to another. 0.1x1000 1000 Explorer 1 ? Don Fairfield and everyone else
Current layer A relative thin layer at the magnetopause where the magnetic field orientation has significant changes. It mostly coincides with where plasma density and temperature varies from one plasma to another. That is where the magnetopause is located. 0.1x100 1000 Explorer 1? ?
Low latitude boundary layer Magnetospheric boundary layers at latitudes near the equatorial plane. It ranges from subsolar region to distance magnetotail. 1x100 1000 IMP 6/?, ISEE/FPE T. Eastman
High latitude boundary layer (Plasma Mantle) Magnetospheric boundary layer at latitudes away from the equatorial plane and antisunward of polar cusps. 1-5x100 1000 ISEE/FPE G. Siscoe
Plasma entry layer Regions sunward of polar cusps. It is a forefont passage that solar wind particles enter the polar cusps. 5x5 100 AMPTE/plasma instrument Paschmann
Polar cusps A pair of plasma regions where the Earth's magnetospheric magnetic field diverges and converges. 1x1 100 Hawkeye ?

Earth's Magnetopause Transient Phenomena

Name Description Spatial scale (Re)Time scale (min) Spacecraft/
Scientists who defined/ agreed with
Reconnection ? 0.1-11-100ISEE/FPE, MAG?
Flux transfer events ? 1-1010-100ISEE/FPE, ISEE/MAGC.T. Russell
Pressure pulses ? 0.1-110-100ISEE/FPE, MAGD Siback
Surface waves ? 0.11-100ISEE/FPE, MAGD. Fairfield, P. Song, S. Chen, etc.

Methodology of Classification:

(1 : weakest ; 5 - strongest)
Name Physical Phenomena Instrumentation Why
Depletion layer 5 5 -
Slow mode transition layer 5 5 -
Magnetopause 5 - -
Field line merging layer 5 - -
Low latitude boundary layer 5 - -
High latitude boundary layer 5 - -
Plasma entry layers 5 - -
Polar cusps 5 - -
Reconnection 5 - -
Flux transfer events 5 - -
Surface waves 5 - -

Influencies on Classification - What distinguish one definition from another:

Research Group

What control the variations of boundary layer properties in time:

(1 : weakest ; 5 - strongest)
Name Solar wind plasma Interplanetary magnetic field Influences
Depletion layer 5 1 -
Slow mode transition layer 5 1 -
Magnetopause 5 - -
Field line merging layer 1 5 -
Low latitude boundary layer 5 5 -
High latitude boundary layer 2 5 -
Plasma entry layers 2 5 -
Polar cusps 3 3 -
Reconnection 2 5 -
Flux transfer events 2 5 -
Surface waves 5 5 -


Chen, S.-H., et al., Exterior and interior polar cusps: Observations from Hawkeye, JGR 102, 11,335, 1997.

Eastman, T. E., The magnetospheric boundary layer: site of plasma, momentum and energy transfer from the magnetosheath into the magnetosphere, GRL, vol 3, 685, 1976.

Eastman, T. E., et al., The boundary layers as the primary transport regions of the Earth's magnetotail, JGR, 90, 9541, 1985.

Fujimoto, M., et al., A geotail observation of low-latitude boundary layer, Adv. Space Res., 20, 813, 1997.

Fujimoto, M., et al., Structure of the low-latitude boundary layer: A case study with Geotail data, JGR 103, 2297, 1998.

Nakamura, M, et al., Geotail observation at the dayside magnetopause - confirmation of reconnection events, Adv. Space Res. 20, 779, 1997.

Gosling, J. T., et al., Plasma flow reversals at the dayside magnetopause and the origin of asymmetric polar cap convection, JGR 95, 8073, 1990.

Paschmann, G, et al., The magnetopause for large magnetic shear: AMTPE/IRM observations, JGR 91, 11,099, 1986.

Paschmann, G, et al., Structure of the dayside magnetopause for low magnetic shear, JGR, 98, 13,409, 1993.

Petrinec, S. M., Geotail observations of magnetosheath flow properties, with simultaneous observations of the solar wind by the wind spacecraft, Adv. Space Res. 20, 767, 1997.

Phan, T.-D. et al., The magnetosheath region adjacent to the dayside magnetopause: AMPTE/IRM observations, JGR, 99, 121, 1994.

Phan, T.-D.,, The low-latitude flank magnetosheath, magnetopause and boundary layer: WIND observations, Adv. Space Res., 20, 809, 1997.

Safrankova, J., Two point observation of magnetopause motion: The interball project, Adv. Space Res. 20, 801, 1997.

Sandahl, I., et al., Cusp and boundary layer observations by Interball, Adv. Space Res. 20, 823, 1997.

Sckopke, N., et al., Structure of the low-latitude boundary layer, JGR 86, 2099, 1981.

Song, P., et al., Structure and properties of the subsolar magnetopause for northward interplanetary magnetic field: Multiple-instrument particle observation, JGR, 98, 11,319, 1993.

Sean (Sheng-Hisen) Chen, Raytheon ITSS
Greenbelt, Maryland
Last update 3/2/2000