HOP 0436

abstract of observational proposal

Main Objective:
Study the long-term evolution of magnetic flux and dynamics of ARs disentangling intrinsic changes from projection effects

Scientific Justification: During the third remote sensing window of the nominal mission phase (RSW3), Solar Orbiter will perform a continuous 4-day monitoring of an active region to study its decay throughout the atmosphere, focusing on dynamics, magnetic flux evolution and moving magnetic features. Specific questions to be addressed are:
- What is the main mechanism of AR decay? Sunspot fragmentation by light bridges? Flux erosion by convective flows? MMFs?
- How is the AR flux dispersed?
- What is the fate of the dispersed flux?

These observations will allow the sources of the slow solar wind at the boundaries of the AR to be studied as well. At the time of the measurements, Solar Orbiter and the Earth will be almost in quadrature, so the AR can be observed from very different vantage points. Ideally, the AR will be located on the western hemisphere, approaching the limb as seen from Earth. It will be observed with Hinode and IRIS for a few days before it disappears beyond the limb and then Solar Orbiter will take over. The coordinated observations will allow the intrinsic flux evolution of the AR to be disentangled from projection effects for the first time, without the need to resort to assumptions on the orientation of the vector magnetic field-

It is expected that Solar Orbiter and Hinode will perform simultaneous observations of the target for at least a fraction of the time. These data will be used for magnetic stereoscopy of the AR.

If no AR is present on the sun at the time of the observations, Solar Orbiter will monitor a coronal hole or network region for 4 days. The final target will be selected three days before the start of the observations.

request to SOT

SP is the main instrument. We request one SP fast map every 6 hours. FOV: 123" x 123", one side, Q75. Total data volume: 680 Mbits/day (4 maps). At the beginning of the Solar Orbiter run, increase the cadence to one map every 4 hours, telemetry-permitting. It would be desirable to take several SP normal maps simultaneously with SO/PHI scans when the AR is very close to the limb, in order to perform detailed comparisons of the AR vector magnetic field from the two vantage points, at similar spatial resolution. One or two SP maps are sufficient for that purpose. The FOV can be reduced as necessary to limit the data volume generated. The exact timings of the PHI observations will be communicated to the Hinode team a few days in advance.

other participating instruments

IRIS requests:
3600010076 | Large dense 320-step raster 105.3x120 320s Deep x 15 | 5343.84 | 6226.33 | 0.80 | 16.7+/-0.1 | 5344+/-0 | 66.8+/-0.0 | 66.8+/-0.0 | 66.8+/-0.0 | 66.8+/-0.0

Low datarate alternative:
3600260076 | Large dense 320-step raster 105.3x120 320s Deep x 15 FUV spectrally | 5266.72 | 4545.33 | 0.58 | 16.5+/-0.1 | 5267+/-0 | 65.8+/-0.0 | 65.8+/-0.0 | 65.8+/-0.0 | 65.8+/-0.0

Additional instrument coordination:
The coverage of the AR will be extended as long as possible back in time using SDO/HMI and AIA observations.

remarks

Dates: Solar Orbiter will perform the AR monitoring from 2022-03-31T17:56:00 to 2022-04-04T16:20:00 (R_SMALL_MRES_MCAD_AR-Long-Term SOOP).
We request Hinode support for 11 days, from 2022-03-24T17:45:00 to 2022-04-04T16:20:00, to extend Solar Orbiter's coverage by 7 days. If telemetry and other HOPs allow, the goal would be to have Hinode start the observations 10 days before Solar Orbiter, i.e., from 2022-03-21T17:45:00 to 022-04-04T16:20:00.
During this time, observations should be taken at regular intervals to provide a complete coverage of the AR evolution. In case of insufficient telemetry, priority should be given to the days just before the Solar Orbiter run.
The observations can be stopped as soon as the AR disappears behind the limb.

Time window: If possible at all, the SP rasters should be started at 05:45 UT, 11:45 UT, 17:45 UT and 23:45 UT every day, to be synchronized with the SO/PHI, SO/EUI and SO/SPICE observations.

Target(s) of interest: Active region in western hemisphere, ideally going beyond the limb after 2022-03-31T17:56:00. If Hinode starts the observations 7 days earlier than Solar Orbiter, an AR near the central meridian would be fine.
If no active region is present on the Sun, a coronal hole or a network cell in western hemisphere with be tracked. The target will be agreed three days before the start of the observations.

Previous HOPs:
The proposer was the PI of HOP 151 "Flux replacement in the solar network and internetwork". This HOP has resulted in 20 refereed papers, two PhD theses and one Master thesis up to now. A complete list of publications can be found at
https://www.dropbox.com/s/jz4a9txtfg3mqkp/HOP151_productivity?dl=0