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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0270

Generation and heating of Network Jets

plan term


@ @


 name : Tian, Landi, DeLuca, Tarbell, Curdt @  e-mail : hui.tian[at]cfa.harvard.edu

contact person in HINODE team

 name : Landi @  e-mail : elandi [at] umich.edu

 abstract of observational proposal
to investigate the generation mechanism and possible heating of the prevalent network jets observed with IRIS

Scientific Background:
IRIS observations have revealed numerous small-scale jet-like features with apparent velocities of 80-250 km/s from the network (Tian et al. 2014). These network jets occur in both the quiet Sun and coronal holes. Their width is often ~300 km or less. Many of these jets show up as elongated features with enhanced line width in maps obtained with transition region lines, suggesting that these jets reach at least transition region temperatures.  The ubiquitous presence of these high-reaching (often >10 Mm) jets also suggests that they may play a crucial role in the mass and energy budgets of the corona and solar wind. SOHO/SUMER observations have revealed persistent blue shifts of upper transition region lines in the network (e.g., Hassler et al. 1999, Peter et al. 1999, Tu et al. 2005, Tian et al. 2009) and these ~5 km/s blue shifts have been widely believed to be signatures of the nascent solar wind or mass supply to the corona. Recently, weak blue wing intensity enhancement of the order of ~2%-5%, suggesting the presence of faint upflows with speeds of 50-100 km/s, has also been reported in the network (De Pontieu et al. 2009, McIntosh et al. 2009). The obvious high-speed jet-like features in IRIS SJI images are also observed in the network, suggesting that they might be closely related to the blue shifts and the blue wing enhancement observed with the earlier instrumentation. The generation of these jets in the network and the accompanying Alfven waves is consistent with the magnetic furnace model proposed by Axford et al. (1992). Although the network jets are observed on the disk and statistically their apparent speeds are twice as large as those of the type-II spicules, it is possible that many network jets are the on-disk counterparts of type-II spicules. Many network jets are also likely the TR equivalent of the rapid blueshifted excursions seen in the chromosphere using CRISP (Rouppe van deer Voort et al. 2009). Type-II spicules have recently been debated as a possible vehicle to supply energy and mass to the corona. In fact, using off-limb observations, De Pontieu et al. (2011) suggested that type-II spicules provide enough mass and energy for heating the corona; on the contrary, Klimchuk (2012) proposed that type-II spicules can only provide a small fraction of the hot coronal plasma. However, a definitive conclusion could not be drawn because of the ambiguities posed by the long line-of-sight affecting off-disk observations. This IHOP is devoted to studying network jets using on-disk observations of IRIS, SDO/AIA, SOHO/SUMER and HINODE: since disk observations are much less affected by line-of-sight superposition, the combination of these three instruments provides a unique opportunity to investigate the generation mechanism and heating of the network jets, and their importance for supplying mass and heating to the corona. The proposed study will also provide new insight into the reconnection process in the interface region, and evaluate the contribution of these high-speed jets to coronal heating and the solar wind.

 request to SOT
NFI: magnetograms over a FOV of at least ~30"x80" at a cadence of ~30 seconds to study the evolution of the underlying magnetic field.  Program 0x4e5 can be used with ROI 1 or program  0x4a6 can be used with ROI 2 set to (0, 25 arcsec South).  If ROI 2 is used, then Hinode pointing for SOT should be 25 arcsec North of the IRIS coordinates.

SP: fast-map before and/or after the IRIS observations start to show the pattern of strong network flux elements in its FOV (~164"x164").

 request to XRT
Use two filters to get a rough temperature diagnostics for the surroundings of jets. Use a starting exposure time as long as allowable. FOV 256" x 256".
Al-poly/Al-mesh for QS
Al-poly-Ti-poly for CH

 request to EIS
ID 175 arm_line_width
Use the 2" slit, an exposure time of ~150 seconds. The core lines are Si VII 275.35, Fe VIII 185.21, Fe XII 195.12 and He II 256.32. Perform a wide raster between the disk center and limb. EIS Study 175 can be used for this observation.

 other participating instruments
Request to IRIS:

IRIS could run one of the following three observations:

a. Very large sit and stare observation. OBS ID is 3844259554 (8s exposure, small line list, SJI 1330).
b. Very large sit and stare observation. OBS ID is 3824263254 (30s exposure, medium line list, SJI 1330/1400).  
c. Very large dense raster observation. OBS ID is 3824263296 (30s exposure, medium line list, SJI 1330/1400).

The target should be coronal hole and quiet sun regions between the disk center and limb. The quiet Sun target has higher priority.

One run needs about 4 hours.  

The target coordinates could be chosen either by the Hinode or IRIS planners, depending on the phase of the Hinode planning cycle.  Better to use the SAA-free periods, but also fine if not possible. IRIS SAA-free times are approximately 11-15 UT and 23 - 04 UT.

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