TitleAttribution of interminima changes in the global thermosphere and ionosphere
Publication TypeJournal Article
Year of Publication2014
AuthorsEmmert, JT, McDonald, SE, Drob, DP, Meier, RR, Lean, JL, Picone, JM
JournalJournal of Geophysical Research: Space Physics
Pagination6657 - 6688
Date Published08/2014
Keywordsionosphere total electron content; solar minimum; thermosphere mass density

We present a statistical attribution analysis of the changes in global annual average thermospheric mass density and ionospheric total electron content (TEC) between the cycle 22/23 solar minimum (which occurred at epoch 1996.4) and the prolonged cycle 23/24 minimum (2008.8). The mass density data are derived from orbital drag, and the TEC data are derived from ground-based GPS receivers. The interminima change in mass density was −36% relative to the 1996.4 yearly average. Considering each multiplicative forcing independently, lower average geomagnetic activity during the cycle 23/24 minimum produced an interminima density change of at least −14%, solar extreme ultraviolet (EUV) irradiance forcing produced a density change of −1% to −13%, and changes in thermospheric CO2concentration produced a density change of −5%. There was essentially no interminima change in global TEC derived from ground-based GPS receivers or space-based altimeters, even though past behavior suggests that it should have changed −3% (0.2 TEC units (1 TECU = 1016 el m−2)) in response to lower geomagnetic activity and −1% to −9% (0.1–0.8 TECU) in response to lower EUV irradiance. There is large uncertainty in the interminima change of solar EUV irradiance; the mass density and TEC data suggest a plausible range of 0% to −6%.

Short TitleJ. Geophys. Res. Space Physics

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