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(mag-nee -tŏ-graf, -grahf) An instrument used to map the distribution, strength, and polarity (direction) of magnetic fields over the Sun's disk. It is usually an automatic scanning system employing instruments to detect and measure the Zeeman splitting of a selected spectral line (see Zeeman effect). The resulting diagram is called a magnetogram.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



an instrument for continuous recording of variations of the geomagnetic field over time (magnetic variations). It consists of magnetic variometers and a recording system. The simplest magnetograph contains a photographic recorder, a light source, and three opticomechanical variometers in which the sensing elements are magnetic needles (with mirrors) suspended on elastic fibers. Such a magnetograph records on a chart (photographic film or paper) the variations of the three orthogonal elements of the earth’s magnetic field with periods of several seconds to several months and an accuracy of the order of 10-5 oersted. The magnetogram thus produced carries information regarding the time, amplitude, and period of the magnetic variations. Magnetometers can be equipped with opticomechanical variometers and photoelectric converters of the angle of rotation of the magnetic needle or with fluxgate, induction, proton, quantum, and superconducting transducers whose electric output signal frequency or amplitude is proportional to the amplitude of the magnetic variation (see Table 1).

Table 1. Characteristics of various types of magnetographs
*1 oersted = 79.6 A/m
Type of variometerSensitivity
Period of
recorded variations
Opticomechanical with photoelectric
10-72 × 10-1-∞
Fluxgate10-72 × 10-1-∞
Induction10-73 × 10-1-∞

The recording devices for such magnetographs may be frequency meters, digital voltmeters with a digital printout device, electric pen recorders, tape recorders, or perforators. The readings of a magnetograph are encoded and processed on electronic computers. The sensitivity of magnetographs depends to a great extent on the technical potential of the variometers used.


lanovskii, B. M. Zemnoi magnetizm [3rd ed.], vol. 1. Leningrad, 1964.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A set of three variometers attached to a suitable recording unit, which records the components of the magnetic field vector in each of three perpendicular directions.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The measurement technique was also the magnetograph one.
The solar wind speed data are obtained from STEL IPS observations, and the parameter B/f is from the calculation of a potential field using Kitt Peak magnetograph observations.
To avoid this, a team at NASA Marshall Space Flight Center in Huntsville constructed a rocket-borne instrument, known as the Solar Ultraviolet Magnetograph Investigation (SUMI), designed to take pictures of these magnetic fields from space.
At the same time a marked decrease in the electric current flowing in the loops was detected by a ground-based magnetograph in Mitaka, Japan.