ESTIMATION OF THE EFFECTS OF GEOMAGNETIC AND SOLAR ACTIVITY ON THE HUMAN BRAIN BIOELECTRICAL PROCESSES WITH STRUCTURAL FUNCTION

: We investigate the impacts of sharp variations in solar and geomagnetic activity (GMA) at high latitudes on the human brain bioelectrical activity by means of the empirical structure function of multi-channel EEG. Ten healthy men ages 19 to 37 took part in the study. EEG was recor- ded daily over the 25 days test period that was marked by C- and M-class solar flares and geomagnetic storm levels in the G2-G3 range. The EEG signals were used for the estimate of the mul-tivariate temporal structure function (SF) of the first order in 8-dimensional space. The value of the SF correlation radius is used here as an estimation of a scale of the integral temporal correlation structure of multi-channel EEG, while the value of the SF horizontal asymptote is used as an estimation of the spatial correlation structure of EEG. It is shown that GMA variations make an even greater impact on the SF correlation radius, than on the SF asymptote. We reveal the disturbing and modulating effects of geomagnetic and solar activity on the SF parameters and its power spectrum. Thus, the SF of multi-channel EEG allows us to estimate the effects of heliogeophysical factors on the integrated brain reaction as a unitary system and may be used to investigate the environmental influence on the humans.