HMI Data Series hmi.Synoptic_Mr_720s - Synoptic Charts - Radial Field

Data Series General Description

The HMI radial field synoptic maps in the data series hmi.Synoptic_M4_720s provide magnetic field for each Carrington Rotation starting with CR 2096 in April, 2010.

The maps are constructed from 720s line-of-sight magnetograms (["hmi.M-720s-info"]). Typically central meridian data from 20 magnetograms collected over a 4-hour interval contribute to each longitude in the synoptic map. The maps collected over a 27-day interval are combined to make a synoptic maps with 3600 longitudes and 1440 steps in sine latitude. [http://jsoc.stanford.edu/data/hmi/synoptic/hmi.Synoptic_Mr.2106.png CR 2106] was constructed from observations taken from January 20 - February 16, 2011.

This data series is the basis for computation of all other HMI synoptic maps

Steps in Constructing the Synoptic Map

Each 4096*4096 magnetogram is first transformed into a 'radial' field map by dividing by the cosine of the angle from disk center, i.e. we assume that the measured field is the line-of-sight component of a strictly radial field.

Next the radial image is transformed into a high resolution map in heliographic coordinates. We exclude about 12 pixels near the limb (r < 0.994) h columns corresponding to tenths of a degree in Carrington Longitude and rows corresponding to equal steps of sine latitude.

Data Series Keywords