HOP 0269

abstract of observational proposal

Background: A Prominence-Coronal Cavity system (PCC) is a large-scale structure in the solar corona that consists of a dense, cool prominence surrounded by a low-density, hot coronal cavity. PCCs are likely manifestations of helical magnetic flux ropes located on the quiet Sun away from active regions (ARs). Their significance lies in the fact that eruptions of PCCs constitute ~40% of all coronal mass ejections (CMEs; Gopalswamy 2006). Therefore, understanding the formation, evolution, and eruption of PCCs is critical to probing the underlying physics of CMEs, a fundamental open question in solar physics.

Motivation: Recent observations from Hinode and SDO have revealed a picture of cyclic mass transport in PCCs, possibly associated with magnetic flux emergence, which may play an important role in a PCC's evolution toward eruption as well as the global chromosphere corona mass cycle (e.g., Berger et al. 2011; McIntosh et al. 2012): (1) Hot, low-density prominence bubbles can expand upward, protrude into the overlying cool, dense prominence, and spawn multiple plumes by the Rayleigh-Taylor instability due to density inversion (Berger et al. 2010, 2011). It was proposed that such hot bubbles, together with other mechanisms, including spicules (De Pontieu et al. 2011; Okamoto and De Pontieu 2011), may supply heated mass and magnetic flux into the corona. (2) Although eventually the coronal mass escapes the Sun as the solar wind and to a lesser extent as CMEs, a sizable fraction of it cools from million degrees to ~10,000 K, due to a runaway radiatively cooling instability (e.g., Karpen et al. 2005), and then returns to the chromosphere. Such cooling condensation can form transient coronal rain (Antolin, Shibata, and Vissers 2010) and persistent prominence drainage (Liu, Berger, and Low 2012, 2014; Berger, Liu, and Low 2012). Coronal condensation may also provide the source of mass that sustains constant downflow streams along filamentary vertical threads in quiescent prominences (Berger et al. 2008; Chae 2010; Schmieder et al. 2010). (3) Finally, Hinode/SOT discovered that PCCs may form by emergence of helical flux ropes as a whole or in part (Okamoto et al. 2008, 2009; Okamoto, Tsuneta, and Berger 2010). All of these new developments highlight a common thread: the formation and evolution of PCCs are regulated by the complex interplay between thermal and magnetic processes involving mass and magnetic flux transport.

Goals: The objective of this HOP is to investigate mass and magnetic flux transport in PCCs and its connection to their eruptions as CMEs. We aim at addressing the following interrelated questions: (A) The cyclic mass transport of both hot and cool plasma in PCCs. What is the physical nature of vertical filamentary downflow threads and enigmatic rising bubbles in prominences? Where, when, and how does in-situ coronal condensation occur? Can we determine the key sources of mass and mechanisms of transport into the PCC that feed the prominence and its drainage? (B) The effect of magnetic flux emergence on PCCs. How does flux emergence develop and affect the formation and evolution of an overlying PCC? Can we associate flux emergence with prominence bubbles? (C) The role of mass and magnetic flux transport in the eventual eruptions of PCCs. Can we correlate mass loss due to drainage in prominences, magnetic flux and helicity build-up by flux emergence below PCCs, or both with imminent eruptions?

To achieve these science goals, we propose a new HOP, by incorporating IRIS, which builds on and extends existing HOPs 73 (Berger et al., Quiescent Prominence Dynamics) and 139 (Okamoto et al., Filament Formation and Evolution by Emerging Flux). Key measurements from individual instruments include: Doppler and plane-of-sky (POS) velocities of off-limb prominences and on-disk filaments by SOT and/or IRIS, density diagnostics of prominences and the prominence corona transition region (PCTR) by IRIS and AIA (EUV absorption), density, temperature, and Doppler diagnostics of the surrounding coronal cavity by EIS and/or AIA, magnetic flux emergence under/near filaments by SOT/SP. The observation specifications described below are organized in two cases: Case 1 for prominences at the limb and Case 2 for filaments on the disk.

request to SOT

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<Case 1 (prominences at the limb)>:

Following HOP 73:

Very high cadence filtergrams and dopplergrams.

FG: Prog. 0x0387
NFI: Halpha 賊208mA DG, 1408x1408, 2x2 sum, 500 msec exposure.
BFI: Ca II H-line, 2K x 2K, 2x2 sum, 1200 msec exposure.
ROI shift for off-limb.
Cadence = 10-20 seconds.

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<Case 2 (filaments on the disk)>:

Following HOP 139:

<Pointing>
Ideal targets: sections of on-disk filaments where/near which signatures of flux emergence can be identified, say, from SDO/HMI magnetograms. If no flux emergence signatures, please set the pointing at the center of a filament in the H-alpha image or at the center of the polarity inversion line in the magnetogram.

Common for all: FOV=100"x82", sum=2x2
SP - Fast map (cycle 2), cadence=repeat
Ca - cadence=4 minutes, Q=65
G-band - cadence=1 minute, Q=65
(A 1-min cadence is necessary for the calculation of the surface flows.)

(A duration of 3-4 hours or more is expected)

request to EIS

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<Case 1 (prominences at the limb)>:

Following HOP 73:
Three EIS studies are requested on each target. The total run time is approximately 3.5 hours. If the total target duration is less than 3 hours, run the studies in priority order according to the list below.

(1) Study 000310: ACRONYM: prom_rast_v1

prom_rast_v1 consists of one raster taking spectra at 80 positions with 1" steps, using the 1" slit, with 50s exposures at each position. It runs in 1h14min, therefore it can be easily inserted in the EIS observing plans. The window height in the Y direction is taken to be 128 pixels, which is sufficient to cover the area occupied by our type of target. JPEG98 compression is used to lower the telemetry requirements. The choice of the 1" slit allows us to aim for maximal spatial and spectral resolution. We observe in 25 spectral windows to have a wide range of lines formed at different temperatures, and allowing several density-sensitive line ratios to be used for plasma diagnostics.

ACRONYM: PROM_RAST_V1
Number of runs: 1
TARGET: Quiescent prominence
EXPOSURE TIME: 50 s
RASTER: scanning
SLIT: 1"
STEP SIZE: 1"
FOV: 81"x128"
RASTER DURATION: 1h14m

The line list is the following:
ID : 149
Acronym : prominence_lines
Author : Nicolas Labrosse
Date : 18-Sep-2008
num Lines : 25

0 180.40 p Fe XI
1 184.24 p Fe X
2 185.21 p Fe VIII
3 186.74 p Fe XII
4 188.23 p Fe XI
5 191.27 p S XI
6 192.82 c Ca XVII
7 193.52 p Fe XII
8 194.94 p Fe VIII
9 196.65 p Fe XII
10 202.04 p Fe XIII
11 203.83 p Fe XIII
12 256.32 c He II
13 257.26 p Fe X
14 258.37 p Si X
15 261.04 p Si X
16 262.98 p Fe XVI
17 264.23 p S X
18 270.40 p Mg VI
19 272.01 p Si X
20 274.20 p Fe XIV
21 275.35 p Si VII
22 277.13 p Si X
23 278.39 p Mg VII
24 280.75 p Mg VII

(2) BL_SUMER_EIS_p2

Number of runs: 1
EIS Window placement: Center just above the prominence. If no prominence is visible center above where prominence would be.
FOV: 2"x400" (100 exp sit-and-stare)
Run time: 1h14m
Objective: characterize the dynamics of the PCTR and cavity with sit and stare.
Data Size: 180 Mb

(3) GDZ_PLUME1_2_300_50s

Number of runs: 1
EIS Window placement: Center just above the prominence. If no prominence is visible center above where prominence would be.
FOV: 300"x512"
Run time: 1h05m per study
Objective: DEM analysis of cavity and PCTR
Data Size: 245 Mb per study

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<Case 2 (filaments on the disk)>:

Following HOP 0149 (Harra et al., Observation of Emerging Magnetic Flux near Disc Centre)

(1) Context:
Context studies to be run at the beginning and end of each observing slot;
Run IUU_SLOT_136x400_Q65, Size: 136 arcsec x 400 arcsec, Duration: 16 minutes, Data volume: 1.3 Mbit

(2) Emerging Flux Observation:
Repeat madj_qs (modified) throughout the observing duration. FoV: 100" X 248", Duration: 32m/raster, Data volume: ~ 450 Mbit/day

other participating instruments

(as of 2020 Feb 10)

IRIS, AIA

[Request to IRIS]

Slit Orientation: if roll is not allowed or restricted by telemetry, the native north-south slit orientation is acceptable.

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<Case 1 (prominences at the limb)>:

Slit length: 175"
Preferred Slit Orientation: vertical to the limb
Rotation tracking: off
Exposure: 15-sec (unless otherwise noted below)

Disk coverage: For the purpose of absolute wavelength calibration, please have a small portion of the slit covering the solar disk, and its majority covering the off-limb region to catch the prominence. To do so, in the IRIS pointing tool, place a corner of the slit FOV box on the disk. Depending on the prominence size and uncertainty in hitting the target, choose 16 or 32-step rasters (the default is the latter to increase the chance of catching a prominence with the slit).

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Prominence OBS IDs:
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Data Rate; Raster steps (cadence)
16-step (262 s), 32-step (296 s/524 s):
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high (0.6/0.7 MB/s): 3610111743, 3610609752 (8-sec exposure)
medium(0.4/0.6 MB/s): 3610611743, 3610111752
low (0.3 MB/s): 3600111743, 3600111752

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<Case 2 (filaments on the disk)>

Rotation tracking: on

Goal: Track the filament evolution over its disk passages, to catch an eruption or flux emergence.

a) Choose suitable obsIDs from the pool below, depending on: (i) the filament's orientation/size and the slit FOV coverage; (ii) use a FOV necessary to cover the full filament (or its majority) and its vicinity.

b) For simplicity, try to stick to one obsID for your week or the entire disk passage of a filament, and avoid switching obsIDs, unless necessary, e.g. because the filament size/orientation has changed, or due to telemetry limitations.

c) If time and telemetry allow, apply roll to achieve more spatial coverage of the filament. (For example, if the target is oriented in a NE to SW direction, use a <0 roll to have the slit roughly aligned with the filament to utilize the larger Y-coverage of the slit than the X-coverage of the raster scan; then a shorter, e.g., a 320-step rather than 400-step raster could be sufficient to cover the full target plus its vicinity).

d) If you need 400-step rasters to cover a long filament, please note automatic solar rotation tracking cannot be turned on. (i) One workaround is to break the observation into blocks and insert the obs of each block individually, by manually setting the pointing obtained from SSWIDL [rot_xy.pro]. Choose the duration of each block so that the solar rotation drift is no more than, say, ~25", which
corresponds to about 3 hours near disk center and much longer near the limb. (ii) Another alternative, at planner's discretion, is to use 320-step rasters that, at the cost of losing some spatial coverage, allow rotation tracking and longer obs (which could be beneficial for long, weekend timelines).

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Filament ObsID Pool:
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Run fast scans: 2x2 binning, FUV x4 binning, small line list
3640604077 (175" slit x 320 steps, 17 min, 0.8 MB/s), 2 sec exposure
3640604078 (175" slit x 400 steps, 21 min, 0.8 MB/s), 2 sec exposure
3640604076 (120" slit x 320 steps, 16 min, 0.4 MB/s), 2 sec exposure
3640604072 (120" slit x 192 steps, 10 min, 0.4 MB/s), 2 sec exposure
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remarks

Target and Sequence Options:

In general, the proposers (Wei Liu or T. J. Okamoto) will help with target selection; otherwise, please follow the guideline below (two options).

(Option-1) Targets of opportunity (stand-alone runs of ideal targets, without long-term tracking):

Run this HOP for 3-6 hours just once, if repeated runs (as described in Option-2) cannot be afforded, and if there is an ideal target, i.e., (A) a long, quiescent on-disk filament with clear signatures of flux emergence (e.g., as indicated by HMI magnetograms), or (B) a large, quiescent off-limb prominence within coronal cavities showing prominence bubbles (as indicated in SDO/AIA 304 A movies).

(Option-2) Continuous monitoring of a target filament/prominence for days:

Initial Target Selection: long, quiescent on-disk filaments, preferentially on the Western hemisphere and with signatures of flux emergence.

Long-term Tracking: once such a target is selected, we request that this HOP (for Case 2, for on-disk filaments) be started and repeated to track its evolution, until it erupts or disappears by other means. If the target rotates to the West limb and becomes a prominence, please follow up with Case 1 (for off-limb prominences).

Duration: prefer 4-6 hr for each run, one run per day, repeated for up to 7 days.

Dates: preferably in eclipse-free seasons for both Hinode and IRIS. Our first choice would be a 4-day run during 2014 October 9-16 when Joten Okamoto, coauthor of this HOP, is the SOT CO. After we learn from this initial run and refine this HOP, the next desired window would be a longer run (e.g., 7 days) during March-April 2015, between the Hinode and IRIS eclipse seasons. Eclipse seasons would be acceptable, although not our first choice.

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References:

Antolin, P., Shibata, K., Vissers, G.: 2010, Coronal Rain as a Marker for Coronal Heating Mechanisms. ApJ 716, 154-166. doi:10.1088/0004-637X/716/1/154.

Berger, T.E., Liu, W., Low, B.C.: 2012, SDO/AIA Detection of Solar Prominence Formation within a Coronal Cavity. ApJ 758, L37. doi:10.1088/2041-8205/758/2/L37.

Berger, T.E., Shine, R.A., Slater, G.L., et al.: 2008, Hinode SOT Observations of Solar Quiescent Prominence Dynamics. ApJ 676, L89-L92. doi:10.1086/587171.

Berger, T.E., Slater, G., Hurlburt, N., et al.: 2010, Quiescent Prominence Dynamics Observed with the Hinode Solar Optical Telescope. I. Turbulent Upflow Plumes. ApJ 716, 1288-1307. doi:10.1088/0004-637X/716/2/1288.

Berger, T.E., Testa, P., Hillier, A., et al.: 2011, Magneto-thermal convection in solar prominences. Nature 472, 197-200. doi:10.1038/nature09925.

Chae, J.: 2010, Dynamics of Vertical Threads and Descending Knots in a Hedgerow Prominence. ApJ 714, 618 足 629. doi:10.1088/0004-637X/714/1/618.

De Pontieu, B., McIntosh, S.W., Carlsson, M., et al.: 2011, The Origins of Hot Plasma in the Solar Corona. Science 331, 55-58. doi:10.1126/science.1197738.

Gopalswamy, N.: 2006, Coronal Mass Ejections of Solar Cycle 23. J. Astrophys. Astron. 27, 243-254. doi:10.1007/BF02702527.

Karpen, J.T., Tanner, S.E.M., Antiochos, S.K., DeVore, C.R.: 2005, Prominence Formation by Thermal Nonequilibrium in the Sheared-Arcade Model. ApJ 635, 1319-1328. doi:10.1086/497531.

Liu, W., Berger, T.E., Low, B.C.: 2012, First SDO/AIA Observation of Solar Prominence Formation Following an Eruption: Magnetic Dips and Sustained Condensation and Drainage. ApJ 745, L21. doi:10.1088/2041-8205/745/2/L21.

Liu, W., Berger, T.E., Low, B.C.: 2014, Coronal Condensation in Funnel Prominences as Return Flows of the Chromosphere-Corona Mass Cycle. In: Nature of Prominences and their role in Space Weather, IAU Symposium 300, 441. doi:10.1017/S1743921313011460.

McIntosh, S.W., Tian, H., Sechler, M., De Pontieu, B.: 2012, On the Doppler Velocity of Emission Line Profiles Formed in the "Coronal Contraflow" that Is the Chromosphere-Corona Mass Cycle. ApJ 749, 60. doi:10.1088/0004-637X/749/1/60.

Okamoto, T.J., De Pontieu, B.: 2011, Propagating Waves Along Spicules. ApJ 736, L24. doi:10.1088/2041-8205/736/2/L24.

Okamoto, T.J., Tsuneta, S., Berger, T.E.: 2010, A Rising Cool Column as a Signature of Helical Flux Emergence and Formation of Prominence and Coronal Cavity. ApJ 719, 583-590. doi:10.1088/0004-637X/719/1/583.

Okamoto, T.J., Tsuneta, S., Lites, B.W., et al.: 2008, Emergence of a Helical Flux Rope under an Active Region Prominence. ApJ 673, L215-L218. doi:10.1086/528792.

Okamoto, T.J., Tsuneta, S., Lites, B.W., et al.: 2009, Prominence Formation Associated with an Emerging Helical Flux Rope. ApJ 697, 913-922. doi:10.1088/0004-637X/697/1/913.

Schmieder, B., Chandra, R., Berlicki, A., Mein, P.: 2010, Velocity vectors of a quiescent prominence observed by Hinode/SOT and the MSDP (Meudon). A&A 514, A68. doi:10.1051/0004-6361/200913477.