The signature of Ca II K grains in the Transition Region and Corona
___________________________________________________________________


Authors:   B. Fleck, S. Steffens, F.-L. Deubner, R. Rutten, 
________   K. Wilhelm (SUMER), R. Harrison (CDS), O. Kjeldseth-Moe (CDS), 
           J. Gurman (EIT)



Progress:            
_________

Discussion at SPWG                     August 25, 1995
First Draft Scheme                     9 May, 1996
1st Revision			       12 July, 1996

 
Scientific Case:
________________

Ca II K ``grains'', sometimes also referred to as ``intranetwork bright
points'', were discovered early in this century by Hale and Ellerman
(1904) who called them ``minute bright calcium flocculi''.  They appear
on Ca II H and K filtergrams and spectroheliograms as bright roundish
dots of approximately 1 to 2 arcsec. They occur within cell interiors
in quiet areas of the solar surface, they are short lived, and they
come and go with 2-5 min intervals (for a comprehensive review of the
Ca II K literature see Rutten and Uitenbroek, 1991). Recent
investigations seem to converge towards a consistent picture in which
the K-grains (or K_2v "flashes") are interpreted as the most prominent
effects (``tops of the icebergs'') of chromospheric shocks governed by
the p-mode interference pattern (Rutten and Uitenbroek, 1991; von
Uexkuell and Kneer, 1995; Steffens et al., 1995). As such, the K grains
are the signature of one of the most dynamic phenomena in the solar
atmosphere. The observed K_3 Doppler shifts often reveal a highly
non-linear wave form with amplitudes approaching the sound speed of 7
km/s (e.g. Hofmann et al., 1996), in good agreement with the
self-consistent radiation hydrodynamic calculations of Carlsson and
Stein (1994). From these calculations the latter authors conclude that
the Sun may not have a classical chromosphere in magnetic field-free
regions (cf.  also Carlsson and Stein, 1995). They showed that enhanced
chromospheric emission, which corresponds to an outwardly increasing
semiempirical temperature structure, can be reproduced by non-linear
wave motions without any increase in the mean gas temperature. They
therefore concluded that the semiempirical chromospheric temperature
rise may be an artifact of temporal averaging of the highly nonlinear
UV Planck function. High resolution UV emission line observations
should provide a clear answer to the questions of whether a
non-magnetic chromosphere does exist or not.

Here we propose a study of the Ca K grain phenomenon and its impact on
the higher atmospheric layers by coordinated observations of the Ca II
K line from ground (Vacuum Tower Telescope (VTT) at Izana, Tenerife)
and selected UV lines from SUMER, CDS, and EIT.  How do these highly
dynamic events show up in optically thin UV lines?  How do they affect
the transition region. Are they related to the C I jets (Dere et al.,
1983, 1986). Do they affect the high temperature corona?  We hope to
find some answers to these and related questions by analyzing
simultaneous, co-spatial high-resolution Ca K and UV line observations,
formed at different levels in the solar atmosphere, from the
chromosphere up to the transition region and hot corona.


References:
___________

Carlsson, Stein: 1994, Oslo Mini Workshop, p.47
Carlsson, Stein: 1995, ApJ 440, L29
Dere, Bartoe, Brueckner: 1983, ApJ 267, L65
Dere, Bartoe, Brueckner: 1986, ApJ 305, 947
Hale, Ellerman: 1904, ApJ 19, 41
Hofmann, Steffens, Deubner: A&A 308, 192
Rutten, Uitenbroek: 1991, Solar Phys. 134, 15
Steffens, Hofmann, Deubner: 1995, A&A 302,277
von Uexkuell, Kneer: 1995, A&A 294, 252




Observing Scheme:
_________________

Pointing: 	- Quiet sun disk center.
	  	- Fixed slit position.
	  	- Rotation compensation ON.



SUMER:
______

		JOP026a:
		========
		Slit: 1*120 arcsec 
		Exposure time: 14.5 s
		Number of frames: 512
		Compression:	5. Quasilog_min_max
		Lines:  O  I  1302.17 A		
			O  I  1306.03 A			
			Si II 1309.28 A 
			C  I  1311.36 A 
			C  II 1334.53 A
			C  II 1335.71 A

		JOP026b:
		========
		Slit: 1*360 arcsec 
		Exposure time: 14.5 s
		Number of frames: 512
		Compression:	5. Quasilog_min_max
		Lines:	Si I 1256.49 A
			N  V 1242.80 A
			O  V  629.73 A
			
		JOP026c:
		========
		Slit: 1*120 arcsec 
		Exposure time: 7.25 s
		Number of frames: 1024
		Compression:	5. Quasilog_min_max
		Lines:	He I    584.33 A
			C  III 1175.59 A			
			O  I   1152.15 A
		
		JOP026d:
		========
		Slit: 1*120 arcsec 
		Exposure time: 7.25 s
		Number of frames: 1024
		Compression:	5. Quasilog_min_max
		Lines:	H I  1025.72 A
			O VI 1031.91 A			
			O VI 1037.61 A
		
		JOP026e:
		========
		Slit: 1*120 arcsec 
		Exposure time: 7.25 s
		Number of frames: 1024
		Compression:	5. Quasilog_min_max
		Lines:	Si III 1298.96 A
			S  I   1300.91 A
			O  I   1304.87 A
			O  I   1306.03 A			


		Each of these 5 sequences (A to E) consists of 3 items:
		- #0 raster scan with 80 smear steps of 1.52" at beginning
		- #1 actual run  
		- #2 full spectrum for calibration purposes (120*1024 px, 98s).
		
		
CDS:
____

		TEST6_1: (for context)
		========
		- 2x240 arcsec slit
		- 120 steps  (-> 240x240" raster)
		- Exposure time: 30 sec
		- Compression scheme: truncate to 12 bits
		- Lines: Si XII 520.67
			 He I   537.03
			 Fe XIV 334.20
			 Fe XVI 335.40
			 Ne VI  562.83
			 Mg VI  349.10
			 He I   584.33
			 O  III 599.59
			 Mg IX  368.10
			 Mg X	624.90
			 O  V   629.73
		
		CA_STUDY:
		=========
		- 2x240 arcsec slit
		- Exposure time: 15 sec
		- Compression scheme: truncate to 12 bits
		- Lines: O  VI  554.52
			 He I   584.33
			 He II  607.56
			 Mg IX  368.06
			 O  V   629.73
		
		MOVIE_CA:
		=========
		- 90x240 arcsec slit
		- Exposure time: 15 sec
		- Compression scheme: truncate to 12 bits
		- Lines: He I  584.33
			 Mg IX 368.06
			 O  V  629.73
		 
		Each day run subsequently: TEST6_1, CA_STUDY, MOVIE_CA.


EIT:
____

Run #1: He 304 high time resolution sequences in a 3x3 block (250x250
arcsec^2), centered on disk center. Temporal resolution: approx. 30 sec




Ground-based (VTT Tenerife):
____________________________

1.) Simultaneous filtergram series with a FOV of 120x120 arcsec^2 in
   	a)  Ca K_2V
    	b)  Mg b_2  
    	c)  H-alpha
    Temporal resolution: approx. 4 sec

2.) Simultaneous time series (scans) in Ca K + Mg b2 (+ slit jaw images).