HOP 0190

abstract of observational proposal

Sunspots are often surrounded by an outflow, the so-called moat. In this moat, small magnetic elements occur which also move outward (Moving Magnetic Features, MMF). Cabrera Solana et.al. (2006) and Sainz Dalda & Martinez Pillet (2005) interpret them as prolongation of penumbral filaments. Sainz Dalda & Bellot Rubio (2008) showed their origin in the penumbra. Some previous investigations find that they move faster than the general moat flow, e.g. Hagenaar & Shine (2005), while Bovelet & Wiehr (2003) report rather small outflow velocities for bright G-band points, which are assumed to be identical with MMFs. Martinez Pillet et al. (2009) report on the discovery of mostly hori-zontal field channels in the 'moat' region that are seen to sustain supersonic flows (line-of-sight component of 6 km/s). The spectral signature of these supersonic flows corresponds to circular polarization profiles with an additional satellite, third lobe of the same sign as the parent sunspot's Stokes V blue lobe, for both downflows and upflows. This is consistent with an outward directed flow that they interpret as the continuation of the magnetized Evershed flow outside sunspots at super-sonic speeds. More systematic studies of how often one finds these satellite spectral signatures surrounding sunspots and their temporal evolution are needed to settle this point. Balthasar & Schleicher (2008) find long lived structures with a Doppler upflow which move outward, but the authors have no information about the magnetic field of these
structures. The aim of this project is to study the magnetic field of MMFs, their Doppler velocity, and their temporal development.

A second topic of our observations will be the search for emerging magnetic loops close to disk center if there are no sunspots on the disk or only very near to the limb. Such loops have been studied only in a very few cases. G"om"ory et al. (2010) observed a single loop and could show that this was a rising omega-like loop. With our setup described below, we can study the development of such a loop in different atmospheric heights. This result does not exclude that descending u-loops also might occur, and profound statistics are missing.

For the topics described above, we plan a coordinated observing campaign with Hinode and the Vacuum Tower Telescope (VTT) on Tenerife. At the VTT, TIP observations in the line groups Fe/Si 1078nm and in Si/He 1083nm in combination with TESOS/VIP observations in Fe 630nm and Ca I 612nm shall be carried out. VIP will provide the 2D information with about one minute cadence needed to localize the MMFs and magnetic loops, while the slit-spectrograph will add high-S/N information on the photospheric magnetic fields in a smaller FOV with a cadence between one and five minutes. The observations should be accompanied by high resolution images in one of the ultraviolet Ca II lines.

Hinode SP maps will deliver context information on photospheric magnetic fields at highest spatial resolution, and Hinode G-band imaging will be used for tatistical studies on size, brightness, lifetime and dynamics of MMF's.

References:
Balthasar,H., Schleicher, H.: 2008, A&A 481, 811
Bovelet,B., Wiehr,E.: 2003, A&A 412, 249
G"om"ory et al.: 2010, A&A, 511, A14
Cabrera Solana et.al.: 2006, ApJ 649, L41
Hagenaar,H., Shine,R.: 2005, ApJ 635, 659
Martinez Pillet et al.: 2009, ApJ,701,79
Sainz Dalda,A., Bellot Rubio,L.: 2008, A&A 481, L21
Sainz Dalda,A., Martinez Pillet, V.: 2005, ApJ 632, 1176

request to SOT

2260 Mbits/day

Combination of SP and FG observations.

SP: Daily observations should start and end with a context SP IQUV scan in fast mode, 123" x 123", 0."32 slit.

2 x 170 Mbits 340 Mbits

Repetitive scans in fast mode, depending on target.

a) Sunspot mode, MMFs:
10."2 x 82", 0."32 slit,
cadence ~2 minutes for two hours,
60 x 10Mbits = 600 Mbits

b) Quiet sun, disk center:
5."1 x 82", 0."32 slit,
cadence ~1 minute for two hours,
120 x 5Mbits = 600 Mbits

600 Mbits

FG: Image series in G-band (430nm) and Ca H with a cadence depending on target. Size: 111" x 111", 2x2 binning

a) Sunspot moat, MMFs:
cadence of 32s for two hours, 1320 Mbits

b) Quiet sun, disk center:
cadence of 32s for two hours, 1320 Mbits

If possible synchronized with the short Sp-scans.

Targets will be moats of sunspots (coordinates will be communicated by the proposer ~40 hours before observation) or disk center. In the MMF-case, the
ideal position for the scans with SP would be just outside the penumbra of a regular spot. The observing procedure is the same for MMF studies and for emerging loop.

If telemetry requires a reduction of the amount of data, we suggest to shorten the duration of the time series but not to change the cadence.

remarks

We request HINODE support for 3 hours every day in the period August 23 -- September 10, 2011, if possible, but partly support will be highly appreciated too. There is no urgent need for several days in a sequence.

The best seeing conditions at Tenerife in August/September are expected between 7:30 and 10:30 UT, therefore we ask to start with the first SP-scan at 7:30 UT. Since the observer at the VTT has to care for the setup in the beginning of the observing period, we put highest priority for coordinated observations to the mid third of the period (week 35), and depending on weather and seeing conditions on Tenerife, lower priority to the last third.

Contact person (at the VTT during the observations) is Horst Balthasar, who will keep daily contact to the HINODE team to specify target coordinates in time.

E-mail: hbalthasar@aip.de
Tel +49-331-7499408 (in Potsdam, until mid of August)
+34-922-329141 (VTT Tenerife).