Equilibrium particle size distributions of the stratospheric aerosol are investigated assuming two production mechanisms. When many stratospheric aerosol particles are produced in the local homogeneous nucleation and are removed by diffusion from the stratosphere (model 1), their size distribution is characterized by three spectral ranges A (r_??_0.01μm), B (0.01μm _??_r_??_0.1μm), and C (r_??_0.1μm). The particles in the range A are controlled mainly by coagulation and the spectrum is proportional to r^-2.75. The particles in the range C grow in size by the attachment with smaller particles and are removed from the stratosphere by sedimentation and eddy diffusion. Coagulation between large particles is negligible because their concentration is small (-1cm^-3). The spectrum in the range C is calculated based on the condensational growth model and is compared with the results of measurements using impactors. The calculation of the spectrum in the range B is not easy because all physical processes are involved, and the spectrum is strongly dependent on the nucleation rate as well as interaction with particles in the range C. This model will be valid when H₂SO₄-HNO₃-H₂O ternary particle formation effectively takes place or where H₂SO₄-H₂O binary formation is activated due to the intrusion of dense water vapor from the upper troposphere near the jet stream or by another air exchange between the troposphere and the stratosphere.
In model 2, Aitken particles transported into the stratosphere from the troposphere or from meteoric flux grow in size by heteromolecular condensation of H₂SO₄-H₂O vapor, and are removed by diffusion from the stratosphere into the troposphere. In this model, which will be valid for the average state of the lower stratosphere even when HNO₃ molecules do not take part in the formation, new particles are not produced in the stratosphere. Concentrations of Aitken particles originated from the troposphere decrease going upwards, and the mean radius of the particles becomes greater. These features are consistent with the measurements of Wyoming group. However the size spectrum of Aitken particles determined by PODZIMEK et al. (1977) does not support model 2 and its shape is similar to model 1. To establish the size spectrum is urgently needed.

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The association of the geomagnetic lunar daily variation (L) in the horizontal component with the polarity of the interplanetary magnetic field (IMF), first detected in the geomagnetic data from an Indian equatorial electrojet station, Trivandrum, is examined with more extensive data of Huancayo, a South American observatory in the equatorial electrojet belt. Seven sets of 4 consecutive years each during the period 1926-61 are selected and the first four harmonics of L are determined separately for days of A and C polarities of IMF in each of the sets, confining the data to the four d-months, November to February, when the signal to noise ratio is largest. In the four sets during high solar activity, C-polarity days show larger L than A-polarity days in the odd solar cycles and vice versa in the even solar cycles which has been noticed earlier in similar results from Trivandrum. The change in response is neither consistent nor significant in the sets during low solar activity. From these results a quasi-stationary double solar cycle, or solar magnetic cycle, in the response of L to the changes in IMF polarity is inferred. The physical mechanisms that may possibly bring about the observed modulation are discussed.

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Noontime absorption on 1.8, 2.0, 2.2 and 2.5MHz at Trivandrum (magnetic dip -0.6°S) can be expressed in terms of solar X-ray and 10.7cm (F_10.7) fluxes and the noontime solar zenith angle by an empirical relation. The components of absorption related to X-ray, F_10.7 and the component independent of these two as obtained from the empirical relation have been examined on the basis of theoretical estimates of contributions to absorption from EUV, X-ray and Lyman-α solar fluxes. The solar activity independent component in the empirical relation is found to agree with the contribution from the solar activity independent component of solar Lyman-α radiation. From the theoretical analysis it has been shown that the wavelength range of solar X-ray effect on absorption for which 1-8Å integrated X-ray flux will be a good representative index is 1Å to 30-35Å.

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Variation in the annual mean value of the north component of the earth's magnetic field from 1964 to 1976 at the Kakioka Magnetic Observatory is examined in relation to variation in sunspot number.
From 1966 to 1973, the annual mean value has shown a decrease at a nearly uniform rate of about 8nT/year with slight fluctuation from which the influence of solar activity on the field may be estimated. At 1965. 5 and in 1974, remarkably large accelerations have taken place which differ considerably from the values expected from the above estimated solar cycle effect. From 1974. 5 the annual mean value began to increase at a rate of more than 10nT/year which is also perturbed by the solar cycle effect. Such abrupt changes in secular variation rate with a time scale of one year or so seem to be worth noting and might be one of the fundamental characteristics of secular variation if it is confirmed by more detailed analysis that it originates in the earth's interior.

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