I am looking for the geomagnetic data for the Indian Ocean region. The 3D data should correspond to longitude-latitude grids at hourly intervals. The model data is easily available at NOAA but I need the observed values (satellite as well as surface observations) for the year 2017. I also checked the NOAA and USGS website but none of them are providing their data for the specific spatial domain.
For surface data, a good place to start is Intermagnet, a global network of geomagnetic observatories. Their data download page lets you filter by time span and region, and sample rates down to the second are available for some observatories. The data are direct observations from individual observatories at fixed locations, and are not averaged over a region. (You mention in a comment that you couldn't find a station for ‘the northern equatorial part of the region near India’; for this region I'd suggest Gan in the Maldives.)
For recent satellite data, the Swarm mission provides an excellent resource. This page gives instructions on how to download their freely available data sets. Registration is required, but as far as I can tell it's free and available to anyone. They've also got an excellent online visualization tool which lets you explore their data interactively.