Magnetic Observatories – Data and Dissemination
India’s participation in pursuing the study of the science of geomagnetism through observations at magnetic observatories initiated in 1836, when the country became a member of the Göttingen Magnetic Union, which was formed in 1836 by Gauss and colleagues. The establishment of the magnetic observatory at Colaba (Bombay) took place in 1841, however, regular observations commenced in 1846. The continuity of the magnetic observations at Colaba is maintained, even after the location was affected by the modernization. This could be achieved by establishing the Alibag observatory, which has its proximity to Colaba. Since its inception, till date contribution of accurate and prompt geomagnetic data from Alibag observatory to the International field of geomagnetic studies is kept up. Establishment of the equatorial and low latitude observatories in India began with the active participation of the Institute in various international collaborative projects.
The geographical location of India in the global scenario is ideal for monitoring the developments in the Equatorial Electrojet activities and its associated effect in the Global Sq current system. The existing extensive network of magnetic observatories through Russia from magnetic pole to peninsular India centered along 145o geomagnetic meridian provides a unique dataset of magnetic variations from pole to dip equator.
Geomagnetic Field Data
Magnetic observatories operated by the Institute are equipped with both modern Digital Fluxgate magnetometers and classical analog recording instruments to record the continuous measurements of the Earth’s magnetic field uninterruptedly. A semi-permanent magnetic observatory is operated at the Indian Antarctic station at Maitri and Bharati. The magnetic measurements from the Indian longitudinal chain form a unique database in view of investigating the ionosphere – magnetosphere-coupling processes, as the entire network can cover the locations spanning equator to the North Pole in the Indo-Russian longitude.
One minute digital data from the Digital Fluxgate Magnetometer (DFM) system installed at magnetic observatories operated by the Institute namely, Tirunelveli, Pondicherry, Visakhapatnam, Alibag, Rajkot, Nagpur, Jaipur, Allahabad, Silchar, Shillong, Port Blair and Gulmarg covering latitudes ranging from equator to Sq focus are received at IIG headquarters in near real time. The absolute measurements at all the stations using high precision Declination Inclination Magnetometer (DIM) and Proton Precision Magnetometer (PPM) are processed to compute respective baseline values and definitive data of one-minute resolution of the DFM system.
The continuous geomagnetic field observations carried out at magnetic observatories of IIG are regularly published for academic/research applications through various platforms. The hourly and one-minute data of the three components of the Geomagnetic field are provided through World Data Centre (WDC) for Geomagnetism, Mumbai (http://www.wdciig.res.in/). The WDC-Geomagnetism, Mumbai is now a member of the new global ICSU WDS.
The near real-time data from the Alibag and Jaipur observatories are processed on daily basis and relayed to INTERMAGNET (http://www.intermagnet.org/), a global network of observatories, monitoring the Earth’s magnetic field. The hourly and one-minute data from the low-latitude station Alibag are transmitted to WDC-Kyoto, Japan (http://wdc.kugi.kyoto-u.ac.jp/) on daily basis and has been used to compute the Geomagnetic storm indices such as Sym-H and Asy-H. Final one-minute absolute values are computed and sent to Paris GIN for inclusion in the annual DVD-ROM published by INTERMAGNET. The magnetic storm sudden commencement amplitudes and ranges computed every month for our magnetic observatories are deposited to World Data Centre, Colorado for inclusion in Geophysical Data Bulletin.