HELIOSEISMIC AND MAGNETIC IMAGER INVESTIGATION
The primary goal of the Helioseismic and Magnetic Imager
(HMI) investigation is to study the origin of solar variability and to
characterize and understand the Sun’s interior and the various components of
magnetic activity. The HMI investigation is based on measurements obtained with
the HMI instrument as part of the Solar Dynamics Observatory (SDO) mission. HMI
makes measurements of the motion of the solar photosphere to study solar
oscillations and measurements of the polarization in a spectral line to study
all three components of the photospheric magnetic field. HMI produces data to
determine the interior sources and mechanisms of solar variability and how the
physical processes inside the Sun are related to surface magnetic field and
activity. It also produces data to enable estimates of the coronal magnetic
field for studies of variability in the extended solar atmosphere. HMI
observations will enable establishing the relationships between the internal
dynamics and magnetic activity in order to understand solar variability and its
effects, leading to reliable predictive capability, one of the key elements of
the Living With a Star (LWS) program.
The broad goals described above will be addressed in a
coordinated investigation in a number of parallel studies. These segments of
the HMI investigation are to observe and understand these interlinked
processes:
These goals address long-standing problems that can be studied by a number of immediate tasks. The description of these tasks reflects our current level of understanding and will obviously evolve in the course of the investigation.
To satisfy the measurement requirements
of the investigation, the HMI instrument will produce filtergrams in a set of
polarizations and spectral line positions at a regular cadence for the duration
of the mission that meet these basic requirements:
In addition, the HMI investigation
will provide sufficient computing capability to convert these raw filtergram
measurements into a set of observables and derived data products that satisfy
the HMI science objectives and that will be made available to all interested
investigators. The primary observables (Dopplergrams, longitudinal and vector
magnetograms, and continuum intensity images) will be constructed from the raw
filtergrams will be made available at full resolution and cadence. Other
derived products such as subsurface flow maps, far side activity maps, and
coronal and solar wind models that require longer sequences of observations
shall be produced and made available.