Executive Summary
The third IACG campaign will make use of the unprecedented constellation of
solar, magnetospheric and heliospheric space missions that the IACG agencies will
have operating in 1996-1998 to produce significant contributions to the study of
solar events - coronal mass ejections (CMEs) in particular. The campaign will
address their origin and development, their propagation through the solar corona
and interplanetary space, and their effect in the Earth's magnetosphere,
ionosphere and atmosphere. It was concluded that in order to achieve a basic
understanding of the disturbance produced by such events it was also necessary to
understand the basic features of the quiet Sun, some of which produce
disturbances in interplanetary space and in geospace of the same order of
magnitude as coronal mass ejections. The same infrastructure used for the study
of the CMEs is needed for the study of the underlying phenomena in the solar
corona and solar wind. The scientific objectives of the campaign are thus the
study of:-
- The "quiet" state of the corona and solar wind including: the acceleration of
the solar wind and the heating of the corona, small-scale dynamics, the coronal
chemical composition, spatial structures in corona and solar wind, mapping the
solar wind to its solar origin, and the dynamics of large-scale coronal loops-
- The origin and evolution of CMEs, including the search for their triggering
mechanisms and their evolution through the corona-
- Propagation of solar variability features through interplanetary space-
- Effects on Geospace, addressing the quiet Sun effects, i.e. those due to
current sheets, and to coronal holes and the resulting high speed solar wind
streams; the disturbed Sun effects, in particular those due to CMEs and those
due to solar flares; and addressing as well the potential applications to
human technology and environment, such as space weather predictions, and
lower atmosphere effects.
The requirements of observations and measurements needed to make progress in
understanding these problems are described for investigations aboard
spacecraft, from ground-based solar observatories (both optical and radio),
and from ground-based geomagnetic observatories.
Due to the large variety of requirements the "campaign" scientific objectives
can be addressed most effectively by dividing it into three "sub-campaigns":
- Quiet-Sun coronal features and their propagation to geospace
- Origin of CMEs
- CME propagation through interplanetary space and effects in geospace.
For sub-campaign (1), a period of about one solar rotation or an appropriate
fraction of it will be selected, to take place by mid-1996, about 7 months after
SOHO launch and as soon as possible to improve the probability that Yohkoh and
Geotail are still operating.
For sub-campaign (2), several "one week" periods of "sit-and-wait" for CME's will
be defined by the SOHO community. The basic plan is to identify a potential CME
source structure as it crosses (W40, and run a diagnostic and monitoring scheme
on that structure for 5-6 days until it is well beyond the limb.
For sub-campaign (3), several approaches are defined: i) One or more periods (a
few days) will be chosen when a CME directed toward Earth is well documented in
SOHO data and when the constellation of Cluster, Wind, Geotail and/or Interball
is favourable. ii) For the study of the CME evolution in interplanetary space,
one or more periods, when a near solar limb CME is well documented with SOHO,
Yohkoh and/or Coronas data and when the Ulysses, and/or Cassini (late in 1997/98)
orbits are favourable for observation. iii) - as a complement to i) - one or more
periods when a large solar flare with associated high energy particles, connected
to the earth, is observed by the core missions.
A full sub-campaign consists of two main phases: 1) coordinated observation and
data acquisition and, 2) coordinated data analysis. Since many of the "in situ"
measurements in interplanetary space will be operating continuously, and since
many solar telescopes are planned to produce periodic full solar images, many of
the observations and measurements required for this campaign will be obtained
automatically without coordination, and some of the sub-campaign periods (most of
the 3rd one) will only consist of a Coordinated Data Analysis Programme of
selected data sets around an observed solar event chosen "a posteriori".
The cornerstone mission for this campaign is considered to be SOHO. We consider that,
taking into account the five months needed for the SOHO transfer to L1 and
commissioning, plus some two months for familiarization with routine operations,
the campaign could start 7 months after SOHO launch (about 1 June 1996).
A
Campaign Coordinator will be responsible for putting together the campaign
details starting about 1 June 1995.
Last Modified:
(G.C.G.)
