Methods for the measurement and ultra-low-frequency evaluation of geomagnetic and ionospheric changes

We present an overview of techniques for the sensing of geomagnetic field changes within the ultra-low-frequency band (1–30 Hz). Variations in the electromagnetic and chemical structure of Earth's surface can lead to altered signals in the frequency region of 6–8 Hz, which is characteristic of the alpha waves of an active brain. In the given context, diverse positive and negative factors influencing the biological system of the human body have been analyzed by research institutes worldwide; our contribution consists in a TM antenna and an evaluation system, both designed using the set of methodologies described within this article.