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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0337

Investigating the role of plasma processes on the stability of solar filaments

plan term


@ @


 name : Jenkins, Long, van Driel-Gesztelyi, Carlyle, Jess @  e-mail : jack.jenkins.16[at]ucl.ac.uk, david.long[at]ucl.ac.uk, lidia.vandriel[at]obspm.fr, jcarlyle[at]cosmos.esa.int, d.jess[at]qub.ac.uk

contact person in HINODE team

 name : Culhane @  e-mail : j.culhane[at]ucl.ac.uk

 abstract of observational proposal
Main Objective:
Investigating the role of plasma processes on the stability of solar filaments

Scientific Justification:
As elongated tubes of cool, dense plasma suspended in the hot solar corona, understanding the formation and evolution of solar filaments requires knowledge of the surrounding magnetic structure which provides the magnetic support for the plasma. Magnetic flux ropes are formed by the continuous emergence and cancellation of small-scale magnetic features along polarity inversion lines (PILs) in the photosphere (Martin et al. 1985; van Ballegooijen & Martens 1989). These small-scale features are interpreted as representing the footpoints of two magnetic flux systems sheared across the PIL. The observed cancellation of magnetic flux leads to the development of these into two (new) distinct magnetic flux systems with a different connectivity to the pre-reconnection pair; a small loop which is pulled below the photosphere by magnetic tension (the observational manifestation of flux cancellation) and a longer, highly sheared loop. The highly sheared nature of this long loop provides a number of dips which can support cool, dense plasma, leading to the development of a tube of filamentary plasma within the flux rope above the PIL as the process of flux emergence and cancellation continues.

In order for this filamentary feature to erupt it must first become unstable, leading either to a coronal mass ejection (CME), or the material collapsing back onto the solar surface as a failed eruption. The loss of stability is thought to be driven by an imbalance between the different magnetohydrodynamic (MHD) forces influencing the filament, namely the upward magnetic pressure and downward magnetic tension. This deviation from equilibrium is explored in each of the breakout reconnection, tether-cutting, and torus instability models. For example, the torus instability (Bateman 1978; Kliem & T ̈or ̈ok 2006) is known to be sensitive to the variation with height of the magnetic field overlying the flux rope (i.e., the decay index). However, the effects of plasma flow within the filament and injection (draining) into (out of) the footpoints of the filament are largely neglected by these models. Despite this, it is known that the effects of the filament plasma can play a key role in deforming the field lines comprising the magnetic configuration on the order of hours (cf. D ́emoulin 1998). Increased plasma flows driven by the change in force balance as the filament rises may also provide an early indication of an imminent eruption. While the results of the eruption of overdense filaments have previously been studied (e.g., Carlyle et al. 2014), the pre-eruption effects of the plasma on the filament are still uncertain, while the sudden loss of stability leading to the eruption is also not very well understood.

 request to SOT
SQT-SP normal map repeated as many times as possible during the observing period to isolate the evolution of the magnetic field along the polarity inversion line.

 request to XRT
Filter: A1poly / Open, FOV: 512h ~ 512h
Exposure time: 8.19 or 16.38
Cadence: 60s

 request to EIS
We request that a single co-alignment run be carried out at the start of the observing period. For this co-alignment we suggest EIS Study 353 (Heavily compressed (Q=50) slot context raster; 488h~488h; 3.5mins). After this we would change to EIS Study 491 (DHB 006) and continue to run this throughout the observation period. The requested observing window will ideally consist of 3-6 runs of EIS Study 491. Finally a single run of EIS Study 353 to again provide context imagery for co-alignment purposes, if sufficient time is available.

 other participating instruments
High data rate:
We request OBS ID 3620259733: - Large coarse 8-step raster 14x120 8s Mg II h/k Deep x 8
FUV spectral - 75.88 - 94.56 - 0.9 - 9.5+/-0.0 - 75.9+/-0.0 - 0.0+/-0.0 - 0.0+/-0.0 - +/-0.0 - 0.0+/-0.0
Low data rate:
We request OBS ID 3620109733: — Large coarse 8-step raster 14x120 8s Mg II h/k Deep x 8
Spatial x 2, - 74.46 - 31.66 - 0.3 - 9.3+/-0.0 - 74.5+/-0.0 - 0.0+/-0.0 - 0.0+/-0.0 - 9.3+/-0.0 - 0.0+/-0.0

DST/NSO: HARDcam2/ROSA: Imagery IBIS: Imaging spectral scans for LOS components FIRS: Spectropolarimetry

SDO: AIA: Co-alignment handler, global context provider HMI: Global LOS field

Dates: 22nd May - 2nd June (2 weeks)
Time window: DST optimal observing period: 15-18 UT (Mid morning DST [UT-7] time)
Target(s) of interest: Footpoint of filament rooted in active region. If no active regions are present with a co-located filament footpoint, the footpoint of a quiescent filament will suffice. Target to be coordinated with DST pointing.

Additional Remarks: We request that the observing plan be run from May 22 to June 2 for 4 - 6 hours centred around 15-18 UT each week day, to coincide with optimal seeing conditions at the DST. Note that the DST does not operate on weekends thus IRIS & Hinode support will not be required on 27 and 28 May.

Previous HOP information:
No previous HOP submissions from this PI

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