JOP098 -- SOHO Joint Observation Programme.

submitted by:
Neale Ranns                 e-mail;  ndrr@mssl.ucl.ac.uk

CDS/EIT/MDI/TRACE/YOHKOH  03-Feb-1999

Multi-Wavelength Observations of Solar Flares.

The principle aim of this Joint Observation Programme is to examine the
morphological and temporal relationships between flare loop footpoint
emissions in Hard X-ray and Extreme Ultraviolet radiation. Flare loop
footpoint emission has been observed up to thirty minutes before a flare
(Cheng,84) and during the impulsive phase (Cheng,81). The impulsive phase
emission was observed to spatially correlate with the HXR emission and the
preflare emission in some examples originated from future flare kernels. 

To accomplish our aim this observing program will incorporate TRACE,
Yohkoh and SOHO-CDS-EIT-MDI in a combined continuous observation of an
active region as it traverses the solar disk. This will ensure the
acquisition of preflare data. Using the wide temporal coverage and high
time resolution of the TRACE instrument we aim to observe EUV brightenings
from Transition region or Chromospheric lines, during the preflare and
impulsive phases of a solar flare and use Yohkoh-HXT to determine the
location of the HXR source. Our intention is to determine the nature of
the preflare burst i.e. whether they are the cause or a consequence of the
X-ray flare. Using the improved spatial resolution of both instruments we
will study the morphological relationships between the EUV and HXR sources
and investigate any relationships between the intensity of the two photon
energy domains. HXT will enable us to accomplish this in a higher energy
band ($53-93keV$) than previously available.

The further employment of SOHO-CDS/NIS, Yohkoh-SXT and SOHO-EIT will
provide information on the densities and temperatures involved within the
flare loops, and with CDS we can measure the velocities of the flare
plasma. Inclusion of the MDI will allow the association of flare kernels
with photospheric magnetic features, and aid with the determination of
loop orientation.


Yohkoh

Continuous tracking of a single active region.

TRACE

Continuous tracking of a single active region. Cycle through filters,
$1550\AA$, $1600\AA$, $WL$ and $171\AA$ to gain high time resolution CIV
and FeIX images.

CDS

Continuous tracking of a single active region. Imaging in FeXVI, FeXIV, OV
and HeI lines.


EIT

Tracking of a single active region, all filters.


MDI

Normal synoptic imaging.