Simultaneous observations of neutral and ionic magnesium in the thermosphere

• Published in: Geophysical research letters Vol. 22; no. 16; pp. 2119 - 2122
• Main Authors: Gardner, James A., Viereck, Rodney A., Murad, Edmond, Knecht, David J., Pike, C. P., Broadfoot, A. Lyle, Anderson, Emmet R.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 15.08.1995; American Geophysical Union
• Subjects: Atmospheric composition. Chemical and photochemical reactions; Density; Earth, ocean, space; Exact sciences and technology; External geophysics; Magnesium; Mathematical analysis; Orbits; Physics of the high neutral atmosphere; Space Shuttle missions; Space shuttles; Tangents; Thermosphere; Thermosphere; Magnesium; Metal; Space shuttle; Magnesium ion; Ultraviolet spectrum
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/95GL01769

Earth‐limb observations by the GLO instrument aboard space shuttle mission STS‐53 include the first simultaneous resonant‐scattering detection of Mg+ (279.6–280.3 nm) and neutral Mg (285.2 nm) in the thermosphere. Although Mg+ emissions are observed in approximately 45% of GLO scans over a wide geographic and local‐time range, neutral Mg is observed in fewer than 1% of the measurements, and most of these sightings occur on two consecutive orbits in a near‐equatorial patch at local dusk. Neutral Mg is observed at tangent heights between 150 and 230 km, with an instrument‐view‐column density of 0.4–1.4 × 108 cm−2, compared with simultaneous Mg+ values of 1.4–5.8 × 109 cm−2. Calculated in‐cloud densities are [Mg+] ∼250 cm−3 and [Mg] ∼5 cm−3, and the average ratio of [Mg+] to [Mg] in the individual measurements is 34:1.