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1984•Geophysical Research LettersRequires access

First measurements of supersonic polar wind in the polar magnetosphere

T. Nagai, Jack Hunter Waite, J. L. Green, Charles Richard Chappell, Richard Christopher Olsen, R. H. Comfort

Open publisher page 159 citations

Abstract

Measurements from the Retarding Ion Mass Spectrometer (RIMS) on Dynamics Explorer (DE) have, for the first time, revealed a supersonic polar wind (Mach number is greater than 1) along polar cap field lines. The observations reported were obtained on the nightside (22:30 to 23:30 MLT) from 65° to 81° invariant latitude and at altitudes near 2 RE. Fitting the data using a thin‐sheath model gives a range of temperatures of 0.1 to 0.2 eV with corresponding flow velocities of 25 to 16 km s−1 over the estimated range of spacecraft potential of +3 to +5 V. For these values the Mach number ranged from 5.1 to 2.6 (with a most likely value of 3). Characteristics of the H+ flow are in general agreement with those predicted by "classical" polar wind theory, but high variability of the He+/H+ ratio was observed.

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What this paper is about

Measurements from the Retarding Ion Mass Spectrometer (RIMS) on Dynamics Explorer (DE) have, for the first time, revealed a supersonic polar wind (Mach number is greater than 1) along polar cap field lines. The observations reported were obtained on the nightside (22:30 to 23:30 MLT) from 65° to 81° invariant latitude and at altitudes near 2 RE. Fitting the data using a thin‐sheath model gives a range of temperatures of 0.1 to 0.2 eV with corresponding flow velocities of 25 to 16 km s−1 over the estimated range of spacecraft potential of +3 to +5 V. For these values the Mach number ranged from 5.1 to 2.6 (with a most likely value of 3). Characteristics of the H+ flow are in general agreement with those predicted by "classical" polar wind theory, but high variability of the He+/H+ ratio was observed.

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Available abstract

Measurements from the Retarding Ion Mass Spectrometer (RIMS) on Dynamics Explorer (DE) have, for the first time, revealed a supersonic polar wind (Mach number is greater than 1) along polar cap field lines. The observations reported were obtained on the nightside (22:30 to 23:30 MLT) from 65° to 81° invariant latitude and at altitudes near 2 RE. Fitting the data using a thin‐sheath model gives a range of temperatures of 0.1 to 0.2 eV with corresponding flow velocities of 25 to 16 km s−1 over the estimated range of spacecraft potential of +3 to +5 V. For these values the Mach number ranged from 5.1 to 2.6 (with a most likely value of 3). Characteristics of the H+ flow are in general agreement with those predicted by "classical" polar wind theory, but high variability of the He+/H+ ratio was observed.

Key concepts: Polar, Mach number, Magnetosphere, Supersonic speed, Physics, Solar wind, Atmospheric sciences, Geophysics

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