Energetics of the Solar Atmosphere T. Metcalf HMI Team Meeting 2003-May-1

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Energetics of the Solar AtmosphereT. MetcalfHMI
Team Meeting 2003-May-1

• The vector magnetic field and velocity can be
  used to understand the energetics of the solar
  atmosphere.
• To measure the free energy requires chromospheric
  data.
• But, the energy and helicity flux across the
  photosphere can be measured with HMI data .
• With good time resolution and continuous coverage
  the energy and helicity input to the atmosphere
  can be computed.

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Motivation

• What is the source of the coronal energization?
• What triggers energy release (e.g. Flares,
  CME's)? Is there an energy or helicity
  threshold?
• What is the source of helicity? What does this
  tell us about the convection zone and the dynamo?
• Do the energy and helicity come primarily from
  below the photosphere or are they generated by
  surface motions?

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Poynting Flux

• The energy flux across the photosphere can be
  measured with HMI data

e.g. Kusano et al.
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Helicity
Helicity
Relative Helicity

• The helicity cannot be observed, but the helicity
  flux across the photosphere can be

See Berger Fields, Demoulin et al., Kusano et
al.
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Kusano's Observations

• Kusano et al. 2002, ApJ, 577, 501

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What do we need for this observation?

• Vector field observations
• Vector velocity observations
• Good temporal resolution to resolve relevant time
  scales.
• Good spatial resolution esp. for correlation
  tracking
• Continuous coverage to integrate changes in the
  energy and helicity
• HMI will be a very good instrument for these
  measurements.