# Presentation: 878642

## Multi-spacecraft observations of polar coronal plumes

- Werner Curdt, Max-Planck-Institut für Sonnensystemforschung

- collaboration of	Klaus Wilhelm
- 			Li Feng
- 			Werner Curdt
- 			Suguru Kamio

**Notes:**
My presentation summarizes the observations of one of the studies carried out during the SUMER/HINODE campaign in April, and the work which has been done so far. I should mention my co-workers, I shouldn‘t say co-workers, since these persons did almost all of the data reduction. I should also mention that there is a poster of this study, and there are more posters from the SUMER/HINODE campaig by Innes, Teriaca, Madjarska

## SoHO:	SUMER		     HINODE:	EIS

- 	CDS					XRT
- 	MDI					SOT
- 	UVCS
- 	EIT
**STEREO**: EUVI A & B	     **TRACE**
**Kitt Peak**: SOLIS

**Notes:**
This study was suggested by Klaus and was supported by many Instruments: on SoHo we had SUMER, CDS, MDI, EIT on HINODE we had EIS, XRT, and SOT. The EUV imagers on both STEREOs did deep exposures. We had TRACE and also ground support from the SOLIS vector magnetograph at Kitt Peak.

But before we come to science I should say a few introductary words.

## EIS and SUMER

- performance parameters:
- spatial:     ~1 arcsec
- spectral:   ~ 2 km/s
- temporal: several seconds

- EIS A: 17 nm < λ < 21 nm
- EIS B: 25 nm < λ < 29 nm
- SUMER: 66 nm < λ < 161 nm

**Notes:**
Since a couple of years it became clear that the remaining life time of SUMER on SoHO would be limited. In the SUMER detectors the gain loss due to the photon load is compensated by raising the HV. In 2003, when we had only one more step to go on the HV, we decided to keep resources and to extend our life time into 2007, when HINODE was in operation. Therefore we had to stop disk observations and go off-limb. Why are joint observations – in particular with the EIS spectrometer - so important? Well, the performance parameters of EIS and SUMER are comparable, but the spectral range is different. EIS observes in the short wavelength range with good lines for the corona and upper TR, while SUMER observes around Lyman-alpha and can see solar plasma from the temperature minimum in the chromosphere to 1 Million Kelvin. We have even hotter lines, but these can only be observed off-disk. It is clear, that both instruments ideally complement each other. With HINODE in orbit, we decided to go back to the disk again, and a campaign was started in April with SUMER HINODE co-observations. About 25 studies were executed at that time. I heard people comparing this to a Kamikaze flight, which it came out not to be the case. During that campaign we collected a huge data set, and only some of the results will be presented here: poster x, y , z, and also this contributed talk about the plume observation. 

## DeForest et al. 1997, Sol. Phys. 175, 393

- Wilhelm et al. 1998, ApJ 500, 1023
- Teriaca et al. 2003, ApJ 588, 566
- Gabriel et al. 2003, ApJ 589, 623
- Antonucci et al. 2004, A&A 416, 749

**Notes:**
Despite of lots of observations polar coronal plumes are still a puzzling phenomenon. The source region is not fully understood, and it is debated whether they contribute to the solar wind, and the formation of plumes is unclear. These are only some papers with those controversial results. At the beginning of April the southern polar coronal hole was well developped, and the pole was pointing towards us by 6 deg: alltogether good observing conditions.

## Slide 5

## West

- East

- view direction B

- view direction A

**0**

**1**

**2**

**3**

**4**

**Notes:**
Stereoscopic images (obtained on 7 April at 22:07) in the 17.1 nm passband of STEREO/ EUVI have been used to reconstruct the position of five plumes in 3D, here shown in epipolar representation (projection onto the south polar plane) in different colours.

The south pole is in the origin, West is up, East is down, this is the limb and these are the view directions of STEREO A and B, projected into the plane.
 Out-of-plane distances (in fractions of R) from 0 to 0.15 are coded by symbol size. The footpoints were found by linear extrapolation of the position onto the Sun. Unfortunately, 3 footpoints are bhind the limb, one is on the limb. The uncertainties are still quite high, in particular for plume 4, because of the small difference in the aspect angles. The geometry should dramatically improve during the next observations planned for October 2007.

## 0

- 1

- 2

- 3

- 4

**O VI     1032, 1038**
**Ne VIII  770**
**Si VIII  1440, 1445**
**Mg IX    706, 750**
**Mg VIII 772**
**Ly-****β****      1025**

**Notes:**
A large raster above the southern CH was obtained in several VUV emission lines. It took 36 hours starting on 7 Apr  at 01:00 UTC in West-East direction. 
Here we show the photon radiance of the O VI line at 103.2 nm. We also transmitted a couple of other lines. There is a clearf plume-interplume signature seen in the raster.
The projections of apparent plume axes are indicated by broken lines.

We have overlayed the plumes found by STEREO to the raster: 0 and 1 fit quite well. It seems as if the SUMER plume has two components

2 and 3 still only match near the footpoint, which may result from the time difference of >12 hours between the EUVI images used for the stereoscopic analysis and the time of data taking in the SUMER raster.

plume 4 can not be used, it is off

## Slide 8

**Notes:**
The radiance ratio of the Ne VIII line at 77.0 nm and the Mg VIII line at 77.2 nm related to the abundance ratio of the high FIP element neon to the low FIP element magnesium clearly delineates several plume structures. Low FIP magnesium dominates the interplume areas.

## 145/140 ratio

-                          Doschek 1997

**Notes:**
The Si VIII line pair at 140/145 nm is density-sensitive, and can be used for an estimate of the electron density. Again, the signature of the plumes is imprinted, and it is clear that N_e is enhanced in the plume by a factor 3 to 5 as compared to inter-plume.

## Slide 10

**Notes:**
Additional observations of the southern CH were taken by the XRT (left) and EIS (right) instruments on HINODE. 
XRT was using the thin Al filter and EIS observed in Fe XII
Several coronal bright points thought to be the footpoints of plumes are clearly seen in soft X-ray and in Fe XII 19.5 nm emission and allow exact co-alignment.

I also added the STEREO plumes to these images. Some of the plumes can be linked to CH bright points seen by HINODE

##    Summary

-  3D plume geometry could be derived from STEREO/EUVI images.
-  Plumes could be linked to CH bright points.
-  Spectral images of the plumes in a wide temperature range.
-  *N*e enhancement in plumes derived from plasma diagnostic.
-  Abundance anomaly in plumes due to FIP effect.
-    _**Outlook**_
-  A second data set, not yet analysed.
-  An ISSI international study team has focussed on this project.
-  Plans for further observations with a better stereoscopic view in Oct.

**Notes:**
To summarize:
- We have been able to derive the 3D plume geometry from STEREO/EUVI images,  although still with significant uncertainties.
- By extrapolation of the plume positions we could link some plumes to CH bright points seen by HINODE.
- We have obtained spectral images of the plumes covering a wide temperature range from transition region temperatures to SXR
- We have applied plasma diagnostics based on line ratios to derive the electron density: N_e is enhanced in plumes
- We have found an abundance anomaly in plumes due to FIP effect: the low-FIP element magnesium is enhanced in plumes

What‘s next:
- We had no time yet to look into other data than shown, no TRACE, no UVCS, no SOLIS.
- We also had no time to look into the other data set obtained a few days later
- The analysis of this interesting data set is still in its early phase. An ISSI International Study Team lead by Klaus aims at revealing the physical processes in polar plumes and interplumes.
- There are plans for further observations with a better stereoscopic view and improved timing later this year.