Micropulsation measurements at low latitudes

Summary Measurements of the geomagnetic field variations performed. at L'Aquila in the range of frequency of micropulsations suggest that the most important events mainly perturb, during daytime intervals, the H-component and show typical periods asT ₁=(25±5)s andT ₂=(13±2)s. These results can be interpreted in terms of a source spectrum peaked atT ₁ together with a resonant mechanism atT ₂ which might correspond to the fundamental eigenperiod of the local field line. Night-time events, with typical periods longer than 40s, basically consist of few cycles of irregular Pi2 pulsations. A comparison with measurements performed at different sites suggest a UT dependence at periods longer than 45s while, at higher frequencies, the power of pulsations might rather be driven by more local magnetosphere and ionosphere conditions. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.