Magnetic storm characteristics of the thermosphere

Abstract

Energy and diffusive mass transport associated with the thermospheric circulation are considered in a self-consistent, though mathematically relatively simple form to describe in a three-dimensional two-constituent model magnetic storm characteristics in composition (N 2' 0, and He), temperature and massdensity. It is shown that during disturbed conditions the latitudinal variations of composition and gas temperature Tg reflect the local nature of the magnetic storm heat input assumed to be primarily confined to the auroral zones. Thereby T g and N2 increase, He decreases and°remains constant through the auroral zones at exospheric heights (due to the superposition of temperature and diffusioneffects) in agreement with OGO-6 mass spectrometer measurements.In contrast, the magnetic storm response in the total mass density is characterized by a strong world-wide component and a relatively insignificant increase toward the poles with the density peak occurring between two (poles) and eight (equator) hours after the maximum energy input, in substantial agreement with satellite drag data. While in situ composition and satellite drag mass-density measurements can thus be reconciled it must, however, be emphasized that the temperature derivation from the satellite drag data cannot be justified during disturbed conditions.

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

“…Large electron densities have been measured with an increase in the O to N 2 ratio (Mayr et al, 1973;Prolss, 1980). But the variation of OI 630.0 nm dayglow emissions versus the O to N 2 ratio is a complex relationship as the reaction rates are altitude dependent.…”

“…This heating also causes an upwelling of the neutral species over the auroral oval, which generates a large wave that is capable of propagating to the magnetic equator in a few hours (Mayr et al, 1978;Prolss, 1993). There are ample evidences of an increase in the neutral temperature and winds at low latitudes during magnetic storms (Mayr and Volland, 1973;Meriwether et al, 1973;Mayr et al, 1978;Prolss, 1980;Burrage et al, 1992;Prolss, 1993;Burns et al, 1995;Fuller-Rowell et al, 1996;Pant and Sridharan, 1998;Fujiwara et al, 1996;Emmert et al, 2001). The thermospheric winds and composition changes are intimately coupled and as a consequence, the F-region electron densities also change accordingly.…”

Global characteristics in the diurnal variations of the thermospheric temperature and composition

“…This effect is more important for He than for 0. Furthermore, the temperature induced variation in the composition, which competes with the diffusion effect and which tends to produce density variations in phase with the temperature, is more effective for the heavier constituent O. with the number of circulation cells (see Mayr and Volland, 1973b). At low latitudes, where the higher harmonics in the diurnal variations are most significant, the diffusion process is thus most effective, causing the phase differences between He, 0, and Tg to increase toward the equator (disregarding the low latitude structures induced by the equatorial anomaly in the F 2 -region).…”

Similarity and differences in morphology and mechanisms of the <i>fo</i>F2 and TEC disturbances during the geomagnetic storms on 26–30 September 2011

“…The way the ionosphere F region and total electron content (TEC) respond to geomagnetic storms is one of the most essential and unresolved issues in ionospheric physics and has been widely discussed for decades (Mayr and Volland, 1973;Mayr et al, 1978;Prölss, 1995Prölss, , 2013Schunk and Sojka, 1996;Buonsanto, 1999;Schunk and Nagy, 2000;Mendillo, 2006). Theoretical studies have been performed using different numerical models of the ionosphere (Pirog et al, 2006;Balan et al, 2009Balan et al, , 2010Huba et al, 2000;Pavlov and Pavlova, 2011), as well as more complex models of the Earth's upper atmosphere (Sojka et al, 1994;Namgaladze et al, 2000;Fuller-Rowell et al, 2007;Lei et al, 2008;Lu et al, 2008;Pawlowski et al, 2008;Klimenko et al, 2011a-c).…”