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General description

This is a study of Active Region heating, developing ideas published in Fludra and Ireland (2008) and Fludra and Warren (2010). The goal is to observe transition region line intensities above magnetic field concentrations in active regions, with simultaneous measurements of the line-of-sight magnetic flux density or vector magnetic field, if available.

Default SOOP duration: minimum 5 hours, but can be run for up to 12 hours.

Target: active region on disk. Preferably small AR with a simple magnetic field configuration. However, any active region to which the PHI instrument is pointed, will be suitable.

Options: Repeated observations on the same active region (several hours apart), or tracking, or pointing to several active regions, are all acceptable modes of observation providing useful data.

Pointing requirements: pointing on disk within +- 30 degrees from disk centre is preferred. Larger off-points reduce the spatial resolution and are progressively less useful.

Observations requirement (baseline)


Medium FOV, medium cadence:

3+ rasters, 3+ hours per . 

  • Slit: 2’’ and 4"
  • Exposure time: 20 s and 10s
  • X positions: 120
  • FoV: 8' x 11'
  • Observation time: 1 hour per raster
  • Nº repeats: 3 – 12  (3 – 12 hours)
  • Ideally, run again on a different AR, or several hours later on the same AR.
Lines:   N IV 76.52 (1 window),  Ne VIII 77.0 (1 window),  SV 78.6+O IV 78.7 (1 window), C III 97.7 (1 window), Ly-beta 102.5 (spectral binning=2 so it becomes 1 window), O VI 103.2 (1 window), CII + O VI 103.7 (2 windows)

HiRes & Full Disk

HRI:  several snapshots at medium cadence, in EUV & LYA  

FSI: FSI  at 30-min cadence, both 174 and 304.


PHI_HRT_NOM_0: HRT nominal mode at any cadence and duration convenient for PHI. 

For example, 5 minute cadence for 2 hours. 

Full disk at 30 min cadence for rest of the time.
Any active region observed by PHI is a good target for SPICE (within the pointing constraints near the central meridian).

Science objectives

SAP objectiveTargetDurationOpportunity
(e.g., orbital requirements, solar cycle phase, quadrature ...)

Operational constraints 

Additional comments
1.2.1 What mechanisms heat the corona?Active Region3-12 hours, repeated several times on different active regionsPreferred near Sun-Earth line to allow SDO and other near-Earth observatories to participate.  However, Solar Orbiter stand-alone observations are also useful and possible any time.

Instances run / planned, differences from the baseline observations

LTP9 (run):

21-25 October 2022 (before AR Long Term Tracking SOOP), 29-31 October 2022 (shorter run, different AR) (SOOP coordinators: A. Fludra)

Science outcomes

Ref of paper using the SOOP data

Original SOOP proposers

A. Fludra, D. Berghmans, J. Hirzberger

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