Second EGSO Use Case

Emergence of an Active Region

Author: J. Aboudarham

Objective:

Follow an active region from the time it appears in the photosphere to its appearance in transition region and corona in order to study its evolution.

Data Sets:

1) Full Sun images (for instance Ha [6563 Å] and Ca II K line [approx. 3980 Å] for chromosphere, EIT 172 Å for low corona, Nançay radiolehiograph data for corona) and magnetograms (MDI) in order to determine interesting new active regions.
2) High resolution visible data and magnetograms (spectral scans) are needed to determine the emergence of the active region, such as THEMIS polarimetric observations of the region in photospheric G-band of Hydrogen (4307 Å) (or any photospheric line sensitive to magnetic field) and Ha data (or any chromospheric line sensitive to magnetic field). Dopplergrams are also of interest.
3) Coronographic and radio observations to follow the evolution of the active region in higher atmosphere.

Data Selection:

• Look for new active regions on full sun magnetograms and images (ie. find active regions then go back to the time just before the active region is first observed – hereafter Time0).
• Look for high resolution polarimetric observations of the region in photosphere and chromosphere at Time0 and for two days.
• Search for the time (Time1) when active region appears in transition region and low corona (from
Time0, during no more than a few days).
• Search for UV and radio data at Time1.

Data Processing during the Selection Phase:

No processing is needed for the data during selection phase.

Data Processing for Selected Data:

• High resolution data must be calibrated (or codes for calibration easily available)
• Data processing of polarimetric observations in order to obtain magnetic field is not needed in my opinion: it is part of the scientific work. But all informations concerning it must be available (such as instrument drift, instrument internal polarization if any, ...)