HOP 0410

abstract of observational proposal

Main Objective: To observe the full solar disk with XRT to identify energetic events that occur near the time of Parker Solar Probe (PSP) perihelion passage, where those energetic events might be the solar source for solar wind features detected in the heliosphere by PSP. IRIS will observe a location suspected to be a likely source location, based on magnetic-connectivity models.

Scientific Justification: During earlier perihelion passages, PSP observed copious disturbances (called “switchbacks”) in the solar wind. The solar source of those disturbances is plausibly in the chromosphere or corona, and various ideas have been proposed, including small-scale reconnection events. We seek to observe such possible events occurring at the footpoints of the magnetic field lines that extend out to PSP at any given time. As the solar source of the disturbances is unknown, we will observe the entire solar disk with XRT at moderate cadence to maximize the chance of pinpointing those source regions, under the assumption that they produce corresponding energetic XRT events. We will use a cool-temperature XRT filter, because the PSP disturbances are very common and therefore expected to originate from cooler-than-flare-temperature events.

IRIS has a more limited FOV than XRT, and therefore its observations will focus on expected likely source locations. The proposers will search for candidate source regions using PFSS or MHD models of the heliospheric magnetic field connectivity. Final targeting information will be supplied to the operations teams beforehand, in accordance with the IRIS and Hinode operational requirements.

This IHOP is a coordinated request from the three groups selected through NASA’s Heliophysics System Observatory Connect (HSOC) program and who plan to coordinate and make use of a wide range of remote-sensing observations. The requested observations will be shared among the HSOC groups to address multiple scientific questions.

This IHOP should be run when activity level is low and the source region is predicted to be in quiet regions or coronal holes. A second IHOP by these same HSOC groups for observations during active periods is also available, and it should be run instead of this one when solar activity levels are high.

other participating instruments

IRIS:
IRIS observations will consist of two raster scans. Scan (1): a longer 320 step very dense raster for context; and Scan (2): a 64 step raster with 4-sec exposures and three SJI filters at 20-s cadence per filter.

During eclipse season (as is the case with the January 2021 perihelion), during the first orbit of the observation period only Scan (1) should run. For the next orbit, only Scan (2) should run, and it should cycle for the complete orbit. This pattern should be repeated, alternating between odd and even orbits, for each day’s set of observations. Outside of eclipse season, Scan (1) should run at the start and end of the period, and Scan (2) should run in between.

Additionally, there are two Options available, A and B. For planning purposes the key factor in deciding between these Options is the duration of Scan (1): The Option-A Scan (1) requires about 27 minutes, and the Option-B Scan (1) requires about 34 minutes. During eclipse season, select Option B if it fits within the Scan-(1) orbit; if the Scan(1)-orbit duration is not long enough for Option B, then use Option A instead.

During non-eclipse season please run Option B at the start and end of the observation period (if observation plans allow).

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Option A:

Scan (1): Context raster with 4 s exposure time for the spectra, spatial x2, spectral x 2 binning, 3 SJI filters (Si IV, MgII h/k, and MgII w) with 20s cadence.

3620106877 | Very large dense 320-step raster 105.3x175 320s Si IV Mg II h/k M | 1651.84 | 1882.89 | 0.78 | 5.2+/-0.1 | 1652+/-0 | 0.0+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0

Low datarate alternative:

3640106877 | Very large dense 320-step raster 105.3x175 320s Si IV Mg II h/k M | 1624.00 | 1139.47 | 0.48 | 5.1+/-0.1 | 1624+/-0 | 0.0+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0

Scan (2): Observation raster with 4 s exposure time for the spectra, spatial x2, spectral x 2 binning, 3 SJI filters (Si IV, MgII h/k, and MgII w) with 20s cadence.

3620106860 | Very large sparse 64-step raster 63x175 64s Si IV Mg II h/k Mg II | 330.37 | 376.58 | 0.78 | 5.2+/-0.1 | 330+/-0 | 0.0+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0

Low datarate alternative:

3640106860 | Very large sparse 64-step raster 63x175 64s Si IV Mg II h/k Mg II | 324.80 | 227.89 | 0.48 | 5.1+/-0.1 | 325+/-0 | 0.0+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0

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Option B:

Scan (1): Context raster with 4 s exposure time for the spectra, spatial x2, spectral x 2 binning, 3 SJI filters (Si IV, MgII h/k, and MgII w) with 20s cadence.

3620106878 | Very large dense 400-step raster 131.7x175 400s Si IV Mg II h/k M | 2064.80 | 2353.61 | 0.78 | 5.2+/-0.1 | 2065+/-0 | 0.0+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0

Low datarate alternative:

3640106878 | Very large dense 400-step raster 131.7x175 400s Si IV Mg II h/k M | 2030.00 | 1424.33 | 0.48 | 5.1+/-0.1 | 2030+/-0 | 0.0+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0

Scan (2): Observation raster with 4 s exposure time for the spectra, spatial x2, spectral x 2 binning, 3 SJI filters (Si IV, MgII h/k, and MgII w) with 20s cadence.

3620106860 | Very large sparse 64-step raster 63x175 64s Si IV Mg II h/k Mg II | 330.37 | 376.58 | 0.78 | 5.2+/-0.1 | 330+/-0 | 0.0+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0 | 20.6+/-0.0

Low datarate alternative:

3640106860 | Very large sparse 64-step raster 63x175 64s Si IV Mg II h/k Mg II | 324.80 | 227.89 | 0.48 | 5.1+/-0.1 | 325+/-0 | 0.0+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0 | 20.3+/-0.0

Additional instrument coordination:
Ground-based support is expected from Big Bear, Sac Peak, and/or Tenerife. Standard data from SDO will be used, including magnetic field data from HMI. Other instruments TBD.

remarks

Dates: This is a target of Opportunity (ToO). It is to be run only around times of PSP perihelion passages, and when activity is low. (During PSP passages with higher activity, the complementary IHOP from the same HSOC teams will be requested instead.) The first such perihelia for this IHOP will be 2021 January 17 and 2021 April 29.

The exact period will depend on the orbital circumstances for each perihelion encounter (i.e. those days when the source region is actually located on the Earth-facing hemisphere of the Sun or at the limb). We focus both on the perihelion date itself, and also the periods several days before and after perihelion when PSP is in near-co-rotation with the solar surface. For the 2021 January 17 perihelion, observations should start 5-7 days prior to that date, and continue for 2-4 days after. For the 2021 April 29 perihelion, observations should start approximately 2 days before that date, and continue for 5-7 days afterward.

Time window: The IHOP should run each of the days of the period over several hours, coinciding with observing times for ground-based observatories. For the 2021 January 17 perihelion, the main observatories will be Big Bear and Sac Peak. If planning permits, the minimum requested period is 15-22 UT, and if possible the period can be extended to 14-23 UT. If operation constraints force a shorter time window, the preference is to start at 17 UT and run for as long as possible (hopefully at least three or four hours).

Target(s) of interest: For XRT: The full solar disk, centered at disk center.

For IRIS: The proposers will notify the Hinode and IRIS teams beforehand of the preferred targeting location.

Previous HOPs:
HOP 339. (Data from that HOP were used in Hanaoka et al. 2018, ApJ, 860, 142.)