HOP 0217

abstract of observational proposal

The main goal of our proposal is to study the families of granules and the photospheric network formation by these families during a long time sequence 24 to 48 hours if possible.

We also plan to observe at the same time (3 to 6 hours) from Pic du Midi over a large field of view (10’x10’) in the G-band with our 4kx4k CMOS camera CALAS (http://ljr.bagn.obs-mip.fr/calas/index.html). The observed families will be compared with the families generated by our new simulation code of the solar granulation developed in our team. We plan also to improve a posteriori ground observation over a large field of view by using simultaneous G-band SOT observations free from atmospheric seeing.

request to SOT

We are interested in observations at the disc center during 24 to 48h if possible, with a time step of 30 to 60 seconds in G-band, with a pixel of 0.16 arc, and if possible magnetograms, blue and red continuum and at least CAII H line. Our estimation of 1 image/minute, which is the minimum time step we need, with a pixel of 0.16 arcsec gives 107Mb/hour and 2.56Go/day. This gives a rate of 237 kb/sec which seems compatible with the mean Hinode rate 300kb/sec. In order to follow the evolution in time of the families properties during the solar cycle, we would be interested by one or two observations per year during the increasing phase of the cycle.

In addition in future proposal, it could be envisaged some observation at two or three latitudes to try to find connection between meridian flow and supergranulation.

request to EIS

We are also interested, if the Hinode rate allows it, to get observations with EIS and XRT every 10 or 20 minutes of the same field of view. This will help to follow the upper chromosphere (He 256A) and corona (FeXV 284A) with EIS during the formation of the photospheric network in the quiet Sun.

Date: Tue, 21 Aug 2012 15:23:21 -0700
From: Ted Tarbell <tarbell@lmsal.com>

Hello, everyone

I had an action item from the last meeting to find out if the ToO HOP 217 (48 hour continuous SOT observation of quiet sun, tracking through disk center) could use an on-disk coronal hole near disk center as its target. If so, then the EIS team was very interested in using the opportunity for CH evolution studies, some time after EUV eclipse season ends.

The answer is affirmative as long as it is reasonably close to disk center, as stated by Thierry Roudier in the following reply:

"Regarding the quiet sun area , I would like the location to be not too far to the disk centre ( to avoid the projection effects). But, I think you can get the best compromise to include part of a coronal hole if it is possible , in order to have EIS observations."

This is not a quantitative answer to how close is close enough, but also remember that the EIS slit is much longer than the SOT FOV (218x109 arcsec). If the top of the SOT FOV just grazed disk center, the bottom would be at theta = 6.5 degrees, and the bottom of an EIS slit ±256 arcsec long centered on SOT would be at 15 degrees. The projection effect at this angle in SOT is very tiny (mu > 0.99), and another 5 or 10 degrees N or S should not be a problem. As an example, pointing SOT at the top of the CH that passed central meridian on August 15, and timing the observation so central meridian came in the center of the interval, would have worked for both instruments, I think:

http://www.solarmonitor.org/full_disk.php?date=20120815&type=saia_00193&region=&indexnum=2

Ted