HOP 0183

abstract of observational proposal

Turbulent flow properties such as vortex formation and shedding are observed in thin sheets within solar prominences (with Hinode) and are described to occur quasi-periodically every few minutes due to thermal and magnetic buoyancy (e.g. Berger et al. 2008, 2010). Bubble-cavities are seen to form below prominences with a possible repetitive pattern over several hours, but the durations of these observations have not allowed confirmation so far. Also related to the thermodynamics and the global stability of prominences are ultra-long period (ULP) oscillations (8-30 hours) detected in EUV filaments (Foullon et al. 2004). Their period increase can be linked to a local ascent of the supporting magnetic field arcade and an increased probability of eruption (Foullon et al. 2009). Any such changes related or leading to prominence eruptions are essential for the evolution of the global corona and space weather.

1) What are the links between the different dynamics (e.g. low-frequency modulations of high-frequency waves)? Can we confirm a repetitive pattern in the bubble-cavities forming below prominences? If so, is this pattern related to the ULP oscillations observed in filaments on the disk?

2) Prominences offer a rich collection of possible instabilities and turbulent regimes (Ryutova et al. 2010). Is there a particular instability that causes the prominence to erupt? Can any of these instabilities coexist, combine or couple?

To answer these questions, we seek coordinated observations from Hinode with STEREO/SECCHI/EUVI and SDO/AIA in order to observe simultaneously the bubble-cavities of prominences on the limb with the EUV observations of filaments on the disk. STEREO/SECCHI/EUVI instruments will provide regular 171 and 195 absorption images, as well as He II 304 images of the filaments. SDO/AIA telescopes provide additional high-cadence context in the EUV, in particular with 171, 193, 304 and 211.

Berger, T. E. et al., ApJ 676, L89, 2008.
Berger, T. E. et al., ApJ 716, 1288, 2010.
Foullon, C. et al., A&A 427, L5, 2004.
Foullon, C. et al., ApJ 700, 1658, 2009.
Ryutova, M. et al., Sol. Phys. 267, 75 2010.

request to SOT

FG: Prog. 0x0387
NFI: Halpha ±208mA DG, 1408x1408, 2x2 sum, 500 msec exposure.
BFI: Ca II H-line, 2K x 2K, 2x2 sum, 500 msec exposure.
ROI shift for off-limb. Appropriate half of BFI FOV centered on the most “sheet-like” region of the prominence.

Cadence = 30�60 seconds. As long as 3 minutes if necessary to run nearly continuously for the full 48 hours. Ideally would include some high-cadence periods within the coverage.

request to XRT

Optimized for cavity observations
XOB#: 1371 (Lin)
Filter : Al/Poly
FOV : 512x512" with 1x1"-res and 2048x2048" with 2x2"-res
Exposure : non-saturated AEC and 4096 msec (fixed) cadence : 30 s and 1 min

Filters and exposure times:
Al-mesh (8 sec)
Al-poly (12 sec)
C-poly (16 sec)
Ti-poly (16 sec)
Al-poly + Ti/poly (23 sec)
thin Be (65 sec)
Cadence: 5 min
Compression: DCPM (lossless)
FOV: 768x768
Binning: 2x2

Note: Long exposure times are requested, but they can be shortened if
bright features exist on the disk and safety of the instrument is an issue.
Cadence can be lengthened to ~10 minutes if necessary for telemetry.

request to EIS

Goal is to obtain imaging spectra in the slot mode with a raster across the prominence at the limb every few minutes. Prominence bubbles are typically 20�50 arcseconds in size. Prominence are anywhere from 50 to 100 arcseconds in length on the limb.
Run for quiescent prominence (preferably polar crown type) at East or West limb
Run HPW004_Q85 (ID # 260) to calibrate slot Te and ne estimates
Run GDZ_LT_JET_SLOT1 (ID # 301); cover ~ 100 arc sec prominence length

EIS slot spectra would ideally be used to diagnose bubble temperature and if possible, density.

remarks

Target

This HOP should be run on quiescent prominences (preferably polar crown type) on the East or West limb. A 48-hour consecutive observation of a large quiescent polar crown prominence at the limb is desired.

To choose a target, keep in mind that if the prominence is visible on the West limb, there should be a filament visible on the Western near-limb disk that will rotate into the prominence over the course of the following day. Similarly if there is a good prominence target on the East limb, STEREO-B should show a filament on its disk with enough length to cover two days of observing.