We review important studies in the field of stratosphere-ionosphere coupling, including recent studies of wave motions of planetary waves, atmospheric tides and internal gravity waves in the atmosphere. The interrelation between stratospheric sudden warmings and winter anomaly of radio absorption, a dynamical model of stratospheric sudden warmings and some production mechanisms of intensified electron density in the D region are discussed. Other topics presented are atmospheric tides in the lower thermosphere including dynamo action, and internal gravity waves, by which we intend to explain travelling ionospheric disturbances in the F2 region and sporadic E layer at midlatitude (wave-enhanced sporadic E). Thermospheric winds are also reviewed and wind effects on the Fz layer are discussed. For each atmospheric event systematic observations of suitable physical quantities with proper time and spatial intervals are desirable.

The effects of the ampere force due to the motion of charged particles on atmospheric tidal oscillations with symmetrical modes in the lower ionosphere are considered with an one-component fluid model using localized Cartesian coordinates. The characteristics of the vertical structures of the oscillations are examined. It is found that for the solar diurnal negative modes resonance phenomena occur at a height of about 115 km. This resonance condition is satisfied when the frequency of the oscillation is coincident with a special frequency. The special frequency is composed of the Coriolis factor and the Hall effect of the charged particle motion in the geomagnetic field. The solar diurnal positive mode and semi-diurnal modes are also discussed.

Senior Research A s s o c i a t e w i t h t h e Goddard I n s t i t u t e for Space Studies: on leave from Kyoto U n i v e r s i t y .2 N 6 7 -3 7 9 2 5 (1) Sq-like c u r r e n t systems changing w i t h u n i v e r s a l t i m e a r e produced and t h e i n t e n s i t y of main vortices i s aboQt one tenth of t h a t of t h e Sq f i e l d f o r a t y p i - i o d i c winds t h e ' m e r i d i o n a l component i s more e f f e c t i v e i n producing c u r r e n t systems. (3) The p o s i t i o n of main curr e n t v o r t i c e s i s c o n t r o l l e d b y t h e d i s t r i b u t i o n s o f ionos-p h e r i c c o n d u c t i v i t y and of wind v e l o c i t y and t h e d e g r e e of i n f l u e n c e of these t w o i s d i f f e r e n t f o r d i f f e r e n t p r o f i l e s of winds. (4) The i n t e n s i t y o f main v o r t i c e s changes w i t h l o n g i t u d e i n such a manner t h a t t h e maximum i n t e n s i t y o c c u r s i n t h e n o r t h and s o u t h American zone and t h e minimum i n t h e A s i a and Oceania zone, b e i n g i n agreement w i t h t h a t of tne Sq f i e l d . (5) N o remarkable d i f f e r e n c e c a n be s e e n i n t h e r e s u l t s o b t a i n e d b y u s i n g d i f f e r e n t c o o r d i n a t e systems.' .

Characteristics of atmospheric tidal oscillations in viscid atmosphere are discussed. When the effect of thermal conduction is included, the equations of the oscillations remain separable with the Hough function as in the classical theory. The vertical structure of the oscillation is given by a fourth-order differential equation. The equation has two kinds of solutions. The one is modified tidal mode and the other is thermal conductive mode. On the other hand, viscous term does not make the equations separable because of the horizontal dependence of the Coriolis force. Approximately, a constant Coriolis force model is used. The horizontal structure is given by the associated Legendre function. The vertical structure is given by a sixth-order differential equation. Two kinds of viscous modes emerge under the Coriolis effect. If the thermal conductive term is also included, an eighth-order differential equation is obtained. Characteristics of the modified vertically propagating tidal modes are that the vertical wavelengths become long and the damping factors become large with increasing kinematic viscosity. The viscous and thermal conductive effects on the nonpropagating tidal modes are to modify their rate of decay to be slightly smaller. The diurnal viscous and thermal conductive modes with negative equivalent heights become important above the height of 140 km because the damping factors decrease with increasing kinematic viscosity, and especially the former mode has similar characteristics to those of the vertically propagating tidal modes. The effect of viscosity on diurnal thermospheric wind is also discussed to investigate the physical meaning of the viscous wave.