TitleLarge variations in the thermosphere and ionosphere during minor geomagnetic disturbances in April 2002 and their association with IMF B y
Publication TypeJournal Article
Year of Publication2006
AuthorsGoncharenko, L, Salah, J, Crowley, G, Paxton, LJ, Zhang, Y, Coster, A, Rideout, W, Huang, C, Zhang, S, Reinisch, B, Taran, V
JournalJournal of Geophysical Research
Date Published03/2006
KeywordsElectron density; thermospheric composition; thermospheric wind

We investigate the variations in the thermosphere and ionosphere using multi-instrument observations during the April 2002 period, with a particular focus on periods during small geomagnetic disturbances. Large and long-lasting reductions in the daytime electron density were observed at midlatitudes by incoherent scatter radars, ionosondes, and GPS receivers. These reductions reached 30–50% and were observed over an extended longitudinal area. They propagated to middle latitudes (35–40°N) in the case of a weak geomagnetic disturbance (Kp = 3−) and to low latitudes (0–10°N) in the case of a stronger disturbance (Kp = 5−). Data from the GUVI instrument aboard the TIMED satellite reveal a reduction in the daytime O/N2 ratio in the coincident area. Similar decreases are also predicted by the TIMEGCM/ASPEN model in both O/N2 ratio and electron density, though the magnitude of the decrease from the model is smaller than observed. We suggest that these ionospheric and thermospheric disturbances result from high-latitude energy input and efficient transport of regions with reduced O/N2 to lower latitudes. We discuss the possible role of a strong positive By component of the interplanetary magnetic field in the transport of regions with reduced O/N2.

Short TitleJ. Geophys. Res.

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