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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0215

Spicules: Current Sheets or flux tubes?

plan term


@ @


 name : Doyle, Madjarska, Nelson, Vanninathan @  e-mail : jgd[at]star.arm.ac.uk

contact person in HINODE team

 name : Culhane @  e-mail : jlc[at]mssl.ucl.ac.uk

 abstract of observational proposal
For a long time spicules have been considered as structures that intermittently couple the chromosphere and the corona through a continuous ejection of mass flux and thereby causing heating. However, the coronal counterparts of these jets were never found, thus the idea of their direct contribution to coronal heating was shelved until recently. Hinode data (De Pontieu et al., 2007) revived this idea when they noted the existence of high velocity spicules which seem to only exhibit upward motion consequently disappearing from the Ca II H
passband images taken with the Solar Optical Telescope (SOT) on-board the Hinode spacecraft. This disappearance was interpreted as heating which causes the singly ionised calcium to become at least doubly ionised. Recently, Madjarska et al., 2011 analysed three large spicules seen in SOT Ca II H images and concluded that these spicules although very large and dynamic, are not present in the spectral lines formed at temperatures above 300,000 K observed with the Extreme-ultraviolet Imaging Spectrometer (EIS) on-board Hinode, hence, questioning whether spicules reach coronal temperatures.

In recent work, Judge et al. (2011) have questioned whether spicules and fibrils are straw-like fine structures (as assumed by most authors) or whether they are best described warps in a sheet. We have obtained DST time to acquire high cadence (1 - 2 sec) IBIS & ROSA data to evaluate the fraction of spicule/fibrils which may be best described by this current sheet. Previous H alpha images taken 27 sec apart clearly shows the formation of a spicule/fibril during the time difference between the two frames implying velocities in excess to 190 km/s, giving Mach speeds in excess of 20. Higher cadence data will allow us to access whether (or what fraction) of these features are jet/tube features or as suggested by Judge et al. as current sheets.

We will have IBIS and ROSA time at DST and will use HMI and AIA data from SDO. EIS data to look at individual spectral lines plus high cadence SOT data will be very important. Already existing and tested EIS studies will be used, a large raster using   madj_ar, plus sit-and-stare (madj_ar_sns_15m) repeated several time to fill the time slot from 14:30 UT to 17:30 UT. High cadence SOT magnetograms (30 sec) will provide crucial information about the magnetic flux involved in these phenomena. The primary pointing will mostly be close to suitable magnetically active features (sunspot or AR or a pore) off disk-center.

 request to SOT
1 hour high cadence SOT magnetograms (Stokes I and V) - 60 sec or better.

 request to XRT
Al_poly filter images with 30 - 40 sec cadence.

 request to EIS
Run first
Followed by
madj_ar_sns_15m (repeat to fill the time slot)

 other participating instruments

The dates for the run are Sept 23 to 30 inclusive.
Time slot from 14:30 UT to 17:30 UT.

The primary pointing will mostly be close to suitable magnetically active features (sunspot or AR or a pore) off disk-center.

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