the daily record of geomagnetic variations at any world location typically shows a multitude of irregular changes in the field that represent the superposition of many spectral components whose amplitudes generally increase with increasing period. it has been a long established fact that variations in ground magnetic records are caused by the dynamo action in the upper atmosphere. these daily v...

We investigated geomagnetic activity which was induced by interplanetary magnetic clouds during the past four solar cycles, 1965–1998. We have found that the intensity of such geomagnetic storms is more severe in solar maximum than in solar minimum. In addition, we affirm that the average solar wind speed of magnetic clouds is faster in solar maximum than in solar minimum. In this study, we fin...

This is anOp Abstract – The oblique ionograms automatic scaling algorithm (OIASA), developed at the INGV for the identification of trace of oblique ionograms, allows the determination of the maximum usable frequency (MUF) for communication between the transmitter and receiver, automatically rejecting poor quality ionograms. A test of the algorithm using data from a campaign of oblique soundings...

From the daily index Ap of geomagnetic activity, sequences of consecutive occurrence of Ap≤4 for four days and Ap≤7 for 8 days are identified in the period 1963-1998. A superposed epoch analysis is performed with the onset of these sequences and with eight different solar wind and IMF parameters. A systematic pattern of change from days preceding to the days following the quiet intervals is cle...

We conduct a statistical analysis of the coherence and phase difference of low frequency geomagnetic fluctuations between two Antarctic stations, Mario Zucchelli Station (geographic coordinates: 74.7 S, 164.1 E; corrected geomagnetic coordinates: 80.0 S, 307.7 E) and Scott Base (geographic coordinates: 77.8 S 166.8 E; corrected geomagnetic coordinates: 80.0 S 326.5 E), both located in the polar...

the electrical conductivity of the earth is its physical parameter, which can be studied in global scales. the investigations of the earth's electrical conductivity are based on geomagnetic field variations. time variations of the geomagnetic field consist of long-term and short-term (transient) variations. external sources induce electric currents into the earth. the induced electric curr...

[1] The short-term relationship between equatorial ionosphere and geomagnetic activity is examined. Hourly averages of the total electron content (TEC) and critical frequency of the F2 layer (foF2) are compared with the Dst index, a proxy for equatorial geomagnetic activity, at three local times (0700–0800, 1200–1300, and 1600–1700 LT) from March 1998 to August 1999. Owing to the geomagnetic la...