SUMER Study #2227: Flare Watch 29.Sep.00

date, time: 29.Sep.00, 08:53 - 30.Sep.00, 07:47 UT
field of view: 980 arcsec E, 400 - 100 arcsec S
slit: 4.0 arcsec x 300 arcsec (number 1)
raster step size: 0.0 arcsec (0 elementary steps)
exposure time: 162.5 seconds
telemetry: 453 images of 512 spectral x 360 spatial pixels (format 38)
compression: quasilog-min-max (method 5)
wavelength: 1108.26 Å on reference pixel 731 of Detector A
rotation compensation: no
binning: no spectral, no spatial
on-board flat field correction: no

During the time of the study, according to the events page, two major flares were observed by GOES: a C3.0 flare at 10:17 UT and a C4.5 flare at 13:13 UT. Both can be seen in the Fe XIX line, followed by a damped oscillation in line shift. Cool (chromospheric or TR) plasma is not present in the flare area, but only in the northern part of the slit. A correlated reaction of cool and hot plasma, very close to the GOES X-ray data of the second (13:13 UT) flare, can be observed approx. five minutes prior to the Fe XIX maximum, but more than 100 arcsec to the north.

Three representative lines were selected for analysis: One relatively cool transition region line, S III + Si III 1113.22 (30 000 - 63 000 K), one coronal line, Ca X 1115.51/2 (740 000 K), and one "hot" coronal line, that only shows up in flare situations, Fe XIX 1118.073 (7 700 000 K). The images below show the SUMER slit with time moving from left to right for approx. 15 hours. Shifts were determined relative to the (not very dynamic) Ca X line.

The Ca X intensity image shows hydrogen absorption in the north of the slit at the beginning of the observation. It also shows that the TR plasma represented by the S III line extends further south. - Approximately two thirds across the SUMER observation, the Ca X image clearly corresponds to the slit position in the EIT image.

The flare reaction in the continuum image at Fe XIX is caused by the huge redshift (around ten pixels). Shift and width development could be influenced by the selected narrow window.

SUMER slit position in EIT image

The small interval shows the position where 10" were averaged for the figures of intensity, shift and width vs. time (see below). Within this interval, the main intensity increases of both reactions take place (px 130-140, i.e. 136"-146" above 400"S; the other reaction at 13:13 UT mentioned above takes place around px 250-260).

Spectral window

Cont 1112 (10 000 K)

S III 1113.22 (63 000 K)

Ca X 1115.51/2 (740 000 K)

Fe XIX 1118.073 (7 700 000 K)

Fe XIX Events in SUMER Study Starting 29.Sep.00, 08:53 UT

Time  Solar X Solar Y    Intensity    Size   Shift   Width
/UT   /arcsec /arcsec   /count s-1 /arcsec /km s-1 /km s-1
----- ------- ------- ------------ ------- ------- -------
10:17    -980    -283      2.93695      46      50      85
10:42    -980    -243      2.70528      58      68      79
11:23    -980    -284      1.19243      45      15      62
11:26    -980    -187     0.470813      35      48      65
11:26    -980    -148     0.741953      45      40      69
13:47    -980    -255      4.42680     150      37      86
17:01    -980    -165     0.488321      20      62      52
21:26    -980    -170     0.245610      30      35      58

Line intensity, shift and width vs. time

Original data are in the (5 MB) IDL/XDR restore file s176402_xdr.rst. It contains the following vectors and arrays:

goes-time    in h after 29 Sep 2000, 00:00 UT
sumer_time   in h after 29 Sep 2000, 00:00 UT
intens_goes  GOES XS 0.5-4 in W / m²
intens_s3    in SUMER count / (line * 162.5 s * px)
intens_ca10
intens_fe19
intens_cont  Cont 1116 in count / (Å * 162.5 s * px)
shift_s3     in km/s
shift_ca10
shift_fe19
width_s3     in km/s
width_ca10
width_fe19
1 px corresponds to 4.0" x (300/287)".

IED, 19.Feb.02