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Behavior of the O+/H+ transition height during the extreme solar minimum of 2008
Author(s) -
Heelis R. A.,
Coley W. R.,
Burrell A. G.,
Hairston M. R.,
Earle G. D.,
Perdue M. D.,
Power R. A.,
Harmon L. L.,
Holt B. J.,
Lippincott C. R.
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2009gl038652
Subject(s) - ionosphere , daytime , sunrise , atmosphere (unit) , atmospheric sciences , equator , altitude (triangle) , physics , environmental science , solar minimum , scale height , equinox , solar irradiance , solar cycle , astrophysics , meteorology , latitude , astronomy , plasma , solar wind , geometry , mathematics , quantum mechanics
Typically the solar radio emission at 10.7 cm is used to scale the critical euv radiation that is absorbed by the Earth's neutral atmosphere. In the latter half of 2008 this radio emission from the Sun was at the lowest levels seen in the last 50 years and the persistence of these low levels has never been recorded before. Here we show that these uniquely low levels of solar radiation produce similarly unique behavior in the Earth's ionosphere and the upper atmosphere. Most remarkably, the altitude extent of the ionosphere is significantly smaller than our present reference models would predict for these levels of solar activity. The transition height resides near 450 km at night and rises to only 850 km during the daytime. At night, this unusually contracted ionospheric shell around the equator has a temperature of only 600 K and prior to sunrise the ion number densities at the transition height fall below 10 4 cm −3 .