On the electrical coupling between the troposphere and the mesosphere

1. Introduction

Figure 1

Figure 2

Figure 3

[2] The studies in both the local and global atmospheric electric circuit arena are an important area of research in atmospheric electrodynamics because the processes acting in the atmosphere are most likely related not only to the variations in the atmospheric conductivity but also to the changes occurring both in the troposphere and in space weather [e.g., Rycroft et al., 2000]. An increased interest in electrical processes in the middle atmosphere has resulted from recent advances in the study of the nature and sources of middle-atmospheric discharges occurring in the upward branch of the global circuit above thunderstorms [e.g., Rodger, 1999] and in the newly discovered effects of atmospheric electricity on the lower ionosphere [e.g., Inan et al., 1996; Rodger et al., 2001]. Unlike the traditional ideas concerning the mesosphere described by, e.g., Bering et al. [1998], it may not be treated as a passive element in the atmospheric electric circuit even under conditions of fair weather, since the inherent current sources [e.g., Aikin and Maynard, 1990; Curtis, 1987; Polyakov et al., 1990; Zadorozhny and Tyutin, 1998] may generate large DC electric fields in the 50- to 70-km region [e.g., Goldberg, 1984, 1989, 1990; Zadorozhny and Tyutin, 1998]. These fields were observed via a few tens of in situ rocket measurements at various sites [Bragin et al., 1974; Croskey et al., 1985, 1990; Hale, 1984; Hale and Croskey, 1979; Hale et al., 1981; Kelley et al., 1983; Maynard et al., 1981, 1984; Tyutin, 1976; Zadorozhny and Tyutin, 1998] (see, e.g., Figure 1) and remotely via a few hundreds of MF radar measurements [Gokov and Martynenko, 1997; Martynenko et al., 1999, 2001; Meek et al., 2004] (see, e.g., Figures 2 and 3). The mesospheric generator sources in the 50- to 70-km region are deduced to be current sources [Martynenko et al., 2001].

[3] Usually, the large DC mesospheric electric fields affect the electron temperature, T_e, and effective collision frequency, n_e, in the ionospheric D region [Martynenko, 1999a, 1999b; Martynenko et al., 2001]; that is, they maintain elevated electron temperatures. This state may change due to the electrical coupling between the troposphere and the electrically active mesosphere. Thus the tropospheric conductivity may undergo a dramatic increase during nuclear power plant accidents with the discharge of radioactive materials [Fuks and Shubova, 1994; Fuks et al., 1997; Martynenko et al., 1994, 1996] or prior to, during, and after earthquakes, when experiments show additional ion production rates attaining sim 7.6 times 10³ cm ^-3 s ^-1 [e.g., Pulinets et al., 1998]. The purpose of this paper is to present a simplified model of a localized electrical coupling between the troposphere, the electrically active mesosphere, and the ionosphere. The model permits the description of the effects of large disturbances in the tropospheric conductivity on the parameters of the ionospheric D region.