HOP 0466

abstract of observational proposal

Main Objective: Plasma flows study inside a Dark Halo by using EIS and IRIS joint observations

Scientific Justification: Solar Active Regions (ARs) are often surrounded by areas appearing less bright than the Quiet Sun (QS), which are called Dark Halos (DHs, Andretta et al. 2014). They were first identified in the chromosphere (Hale & Ellerman, 1903) but with the advent of UV and EUV observations it has been possible to observe regions of reduced emission around ARs also in a wide range of spectral lines originating Transition Region and low corona. DHs are very common solar features, yet we do not fully understand what they are or the physical mechanisms that create and sustain them.

This study will investigate the relationship of DHs with AR upflows/downflows, which has not been done yet. We want to study Doppler shift maps of a DH in order to examine the plasma velocities inside it, by combining Hinode/EIS and IRIS simultaneous observations, that together allow a view of the solar atmosphere from the chromosphere to the corona.

request to EIS

EIS observing sequence would consist of one run of Full Sun Spectral Sun (study ID #544) followed by one run of dhb_Spectral_atlas_covering_30x160_with_2"_slit_120s_exposures (study ID #468) on the same target. Ideally, this sequence should be repeated every two days times during the transit of the Active Region on the disk, in order to monitor the target at different heliocentric angles, included near the limb.
The specific targeting of study #468 observations should be arranged with the proposers each time.

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EIS Study 1 Detail:
Full Sun Spectral Sun DHB_007 (study ID #544)
TARGET: Outskirts of Active Region
EXPOSURE TIME: 30s
RASTER: Scanning
NO. OF POINTING POSITIONS: 123
SLIT: 2”
STEP SIZE: 4”
WINDOW HEIGHT: 512 pixels
RASTER DURATION: 3690s
LINE LIST (ID #544)
Ion species Wavelength Default widths
(A) (pixel)
FeXI 180.40 32
CaXV 182.10 32
FeX 184.33 32
FeVIII 185.21 24
FeXII 186.75 32
FeXI 188.40 48
CaXVII 192.47 56
CaXIV 194.10 40
FeXII 195.12 24
FeIX 197.86 24
CaXV 201.05 24
FeXIII. 202.04 24
FeXIII 203.83 24
CaXVI 208.50 32
SXIII 256.48 32
SiX 258.37 24
SiX 261.04 24
FeXVI 262.98 24
SX 264.30 72
FeXIV 270.52 24
SiVII 275.40 24
MgV 276.30 40
MgVII 278.40 24
MgVII 280.39 56
FeXV 284.16 24
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EIS Study 2 Detail:
dhb_Spectral_atlas_covering_30x160_with_2"_slit_120s_exposures (study ID #468) on the same target
EXPOSURE TIME: 120s
RASTER: Scanning
NO. OF POINTING POSITIONS: 30
SLIT: 2”
STEP SIZE: 2”
WINDOW HEIGHT: 160 pixels
RASTER DURATION: 3600s

LINE LIST (ID #544)
Line Wavelength Default widths
(A) (pixel)
CCDBSHRT0 177.54 1024
CCDBLONG0 200.37 1024
CCDASHRT0 257.02 1024
CCDALONG0 279.81 1024

remarks

Dates: The observation should capture a portion of the dark halo at different stages of the Active Region transit on the disk. As a consequence, ideally the instruments (EIS, IRIS and XRT) should run the observing sequences multiple times, ideally once per day during the transit of the corresponding Active Region on the disk.

Time window: The observation should follow the transit of the Active Region on the disk, therefore the time window should be of approximately 10 days. During the observing periods short interruptions should be avoided.

Target(s) of interest: The target is an extended region of low emission (lower than the Quiet Sun) located at the outskirts of an Active Region (AR), typically outside the AR core as observed in SDO/AIA 171 A waveband and clearly visible in this same waveband. Ideally, the AR selected for the observation should be a young simple bipolar active AR. In addition, it should be as isolated as possible and distant from other ARs.

Previous HOPs: No prior HOP submissions