Heat conduction waves in the upper atmosphere

Abstract

In the thermosphere a temperature and pressure disturbance of the neutral air can be transported vertically by a wave mode that mainly depends on the heat conductivity of the air. In the low‐frequency region (ω < 10−2 sec−1 or periods of τ > 10 min) these heat conduction waves propagate with phase and group velocity proportional to the reciprocal density of the air. The mean velocity is of the order 10–100 m/sec within the ionospheric F region. The traveling time of a disturbance from the exosphere down into the lower F region is about 10 hours and about 2 days down into the E region. These waves may be excited by hydromagnetic waves in heights above 1000 km. Their large propagation time can explain the time delay of ionospheric storms and of the geomagnetic activity effect of the neutral air, as well as the after‐storm effect of VLF phase heights in the nighttime E layer related to the time of impact of an enhanced solar wind as the beginning of a geomagnetic storm. Moreover, heat conduction waves may be the cause of ionospheric traveling disturbances excited within the exosphere and propagating downward with a phase velocity equally directed to their group velocity.

Density Perturbations in the Upper Atmosphere Caused by the Dissipation of Solar Wind Energy

“…Third, partial ring currents closing in the ionosphere were made responsible for Joule heating in the subauroral region (Cummings and Dessler 1967;). Finally, charge exchange interactions within the ring Table 1 Heat sources for the disturbed upper atmosphere discussed in the literature (1) Absorption of solar high-energy electrons (b rays) Petersen (1927a, b) (2) Absorption of a flash of solar ultraviolet radiation Maris and Hulburt (1929a, b) (3) Joule heating by (sub)storm currents Chapman 1937, Cole (1962a (4) Absorption of solar audio-frequency waves Menzel and Salisbury (1948) (5) Heat conduction from the disturbed solar corona Chapman (1959) (6) Heating by solar corpuscular radiation Jacchia (1959) a (7) Energy deposition by storm-generated MHD waves Dessler (1959a, b), Nicolet (1962) (8) Joule heating by currents induced in loops of magnetospheric flux tubes exposed to the variable interplanetary magnetic field Krassovsky (1959) (9) Heat input by precipitating auroral particles Ishikawa (1959), Bates (1960), Chamberlain (1961) (10) Viscous heating by gravity waves generated in the polar upper atmosphere Gold, in Hines (1965) (11) Heat conduction from the ring current Cole (1965) (12) Absorption of energetic ions precipitated from the ring current Galperin et al (1966) b (13) Viscous heating by gravity waves generated in the middle atmosphere Newell (1966) (14) Joule heating by partial ring currents closing in the ionosphere Cummings and Dessler (1967) (15) Heat addition by heat conduction waves excited by MHD waves Volland (1967) (16) Absorption of neutralized energetic ring current particles Krassovsky (1968) (17) Direct absorption of solar wind particles in the cusp region Olson (1972) a This heat source had been considered earlier in ionospheric storm studies (see Martyn 1953) b Earlier, the outer radiation belt had been considered a potential heat source of the quiet-time upper atmosphere (e.g. Van Allen et al 1959;Jastrow 1960) current belt generate a continuous flux of energetic neutral atoms (ENAs), part of which impinges upon the upper atmosphere (Dessler et al 1961).…”

Upper atmospheric response to transient heating

“…This is taken into account automatically in the isobaric frame, as may be seen by the presence of p(•, t) and not p, ($, t) in equation 26. Volland [1967] has shown that vertical forces due to ion drag and viscosity are small corn- [Jacchia, 1966;Roemet, 1967]. The success of the models in predicting the general altitude dependence of the perturbation suggests that the heating from solar EUV and the geomagnetic effect occurs in roughly the same effective altitude range (150-200 Inn).…”