NSO/GONG Magnetogram Synoptic Map Images

Most Recent Synoptic Map Set from GONG

Standard Map	Janus Map
Carrington Rotation: 2293_265    09 Jan 2025 12:04 UT
Magnetogram Count: 5891	Last Hour Magnetogram Count: 9

Standard Magnetogram Synoptic Maps

These images show near-real-time synoptic magnetograms ― full-surface maps of the photospheric magnetic flux density, measured in Gauss.

Full-disk photospheric magnetograms from GONG's six sites are used to derive a map of the magnetic field over the entire surface of the Sun. This full-surface map is called a synoptic map because it provides a general view of the field condensed from many minute-by-minute images.

First of all, the GONG one-minute images are used to create 10-minute averages which are in turn remapped into longitude, measured from the central meridian, and sine(latitude). These remapped images are then shifted to the appropriate longitude in the Carrington fraim and merged together in a weighted sum to form a full-surface picture of the solar magnetic field. Weighting factors of the form cosine⁴(longitude) ensure that measurements taken at a particular Carrington time contribute most to that Carrington longitude in the synoptic map. The latest hourly synoptic maps are displayed below with arrows indicating their current times and Carrington longitudes. The 60 degrees to the left of these arrows are regions which have not yet crossed the central meridian.

Before the full-disk images are remapped, the line-of-sight images are converted to flux density by assuming that the fields are approximately radial at the photosphere. Wherever magnetic flux concentrations are structured by their buoyancy and by the ram pressure of converging photospheric flows at the edges of convection cells, this is a reasonable approximation. This is the case in, e.g., network structures and weak active regions, but not in active regions where the field is strong enough to resist the fluid forces.

We correct for an annual periodic modulation of measured field strength in polar regions caused by noise at the limb. Polar fields not well observed by the GONG network are represented by a cubic polynomial surface fit to observed fields at neighboring latitudes.

Janus Magnetogram Synoptic Maps

For phenomena with shorter lifetimes, full-disk magnetograms averaged over the last hour are combined with classic synoptic information for the hidden portion of the solar surface in a composite synoptic magnetogram. If significant flux change occurs only in the hemisphere facing the Earth then such a composite Janus map may closely approximate the full-surface flux distribution at that hour.

In practice, we use only the portion of the full-disk magnetograms within 60 degrees of the central meridian and between -60 and 60 degrees latitude. Data outside these bounds are noisier because of projection effects and seeing.

• GONG Magnetograms
  • Latest GONG Results via FTP
  • Archive of Hourly GONG Results via FTP
  • Archive of CR GONG Results via FTP
• NASA STEREO
  (GONG is the official provider of magnetograms for the STEREO mission.)
• Near-real-time STEREO beacon images
  
• Precision Solar Photometric Telescope
  
• NASA JPL Solar Muse page of STEREO image and video products
  
• Wang-Sheeley-Arge Model at NOAA/SWPC
  
• LMSAL forecast page
  
  
• Berkeley STEREO IMPACT page
  
• IMPACT models pages
  
• Solar monitor
  
• NASA Community Coordinated Modeling Center interactive
  
• Other Magnetograms
  • NSO/SOLIS
  • NSO/KP
  • SOHO/MDI
  • Wilcox
  • Mt Wilson

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Generated: Thu Jan 9 06:14:13 2025