Note on the dependence of Pc3-4 activity on the solar wind velocity

Abstract. Various models that describe the dependence of pulsation amplitude A on the solar wind velocity V are discussed. Phenomenological considerations and experimental data count in favour of a model of the form A/A₀=(V/V₀) exp (-V₀/V). The linear model A=a+bV which is common in the literature gives negative values of amplitude as V->0, which is strange from the physical point of view. The possibility of modifying the linear model by including critical phenomena is discussed.