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Magnetograms are maps of the observed solar magnetic field in the photosphere. The line-of-sight component of the field can be accurately measured as it evolves in time over the full visible disk of the Sun. The HMI instrument exploits the Zeeman effect, which allows the strength of the line-of-sight component of the magnetic field to be determined by measurements of the spectral line in circularly polarized light.
HMI makes two independent measurements of the line-of-sight component of the photospheric magnetic field. One is collected every 45 seconds with the HMI Doppler camera. The other is computed every 720 seconds using filtergrams recorded by the Vector Field camera. The spatial resolution is 1 arc second (half arc-second pixels) and the full disk images are collected on a 4096**2 detector. The noise level is nominally between 5 and 10 Gauss. HMI really measures flux density in Mx/cm2 in each pixel.
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Added ResourceType and NamingAuthority. Changed http to https in top-level schemaLocation attribute. Fixed version number separator in top-level schemaLocation attribute. Matched version number in schemaLocation attribute to updated value in Version tag. ZCB
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2025-09-30 14:25:18Z
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Updated PublishedBy name to match ROR Registry. ZCB
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2025-12-04 13:31:26Z
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Added MetadataRightsList. Updated to 2.7.1. ZCB
Description
Magnetograms are maps of the observed solar magnetic field in the photosphere. The line-of-sight component of the field can be accurately measured as it evolves in time over the full visible disk of the Sun. The HMI instrument exploits the Zeeman effect, which allows the strength of the line-of-sight component of the magnetic field to be determined by measurements of the spectral line in circularly polarized light.
HMI makes two independent measurements of the line-of-sight component of the photospheric magnetic field. One is collected every 45 seconds with the HMI Doppler camera. The other is computed every 720 seconds using filtergrams recorded by the Vector Field camera. The spatial resolution is 1 arc second (half arc-second pixels) and the full disk images are collected on a 4096**2 detector. The noise level is nominally between 5 and 10 Gauss. HMI really measures flux density in Mx/cm2 in each pixel.
PublicationInfo
Authors
The HMI Consortium: Stanford University (USA); NASA Goddard Space Flight Center (USA); Lockheed Martin Solar and Astrophysics Laboratory (USA); National Center for Atmospheric Research (USA)
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