Micropulsation Instrumentation Systems at the Dallas Geomagnetic Center

Scientists from the Graduate Research Center of the Southwest, Texas Christian University, and Texas Instruments Incorporated are conducting theoretical and experimental studies of the effects of magnetohydrodynamic (MHD) waves on low-frequency (10-4 to 100 cps) fluctuations in the earth's electromagnetic field (often called micropulsations). The experimental part of the program involves the operation of an observatory for the sensing and collection of micropulsation data. This micropulsation observatory, together with a U. S. Coast and Geodetic Survey Standard magnetographic observatory, are collectively known as the Dallas Geomagnetic Center. The magnetic field changes in N-S and E-W geomagnetic directions are sensed by means of induction coils with six foot long mu-metal cores, short iron core coils, an Automatic Standard Magnetic Observatory (ASMO) which uses a rubidium vapor magnetometer, and by standard magnetographs. Corresponding electric field changes are sensed by electrode pairs buried in the Earth a few hundred feet apart. The data which consists of recordings of fluctuations in the earth's magnetic and electric fields in a range from a few cycles per month to a few cycles per second (cps) is available in the form of reproducible paper charts, analog magnetic tape, digital magnetic tape, and punched paper tape, or IBM cards.