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REPORT FROM THE CONVENORS OF CHAPMAN CONFERENCE ON MAGNETIC STORMS
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From: Bruce Tsurutani (BTSURUTANI@jplsp1.jpl.nasa.gov)

More than 100 scientists from 20 countries met at the Jet Propulsion
Laboratory, Pasadena, California, during the week of February 12-16,
1996, to discuss recent developments of research on magnetic storms.
In spite of the importance of magnetic storms in the science of
Solar-Terrestrial relationship, surprisingly this was, to our knowledge,
the first large-scale international conference on this topic ever held.
A press conference was held followed by an article in Science.

The conference focused on many different aspects of magnetic storms,
starting with its origin at the Sun and in the interplanetary medium,
followed with the storm dynamics and structure in magnetospheric and
ionospheric regions, and ending with studies about its main atmospheric
and ground effects. The present efforts to forecast its occurrence
were also discussed. Twenty invited review talks covered a vast
number of topics, addressing not only tutorial perspectives but also
very recent unpublished research contributions. The invited talks
will be published as a special Monograph of the American Geophysical
Union.

These review talks were complemented by about one hundred contributed
(oral and poster) papers, many of which will be published in a special
issue of the Journal of Geophysical Research - Space Physics (with
regular review procedures). The editor of the special JGR issue (Y.
Kamide) also welcomed papers on magnetic storms by authors who had
not participated in this Chapman Conference.

SOLAR AND INTERPLANETARY PROCESSES. Certainly our ultimate answer
about the origin of geomagnetic storms resides in the knowledge of
associated solar and interplanetary processes. Toward this search,
in this Conference important new clues were unveiled among the
review and contributed papers. T. Kosugi presented new evidence for
magnetic reconnection at the solar corona using YOHKOH images, both
for active region-scale lengths and for larger regions at the solar
corona, probably related to CMEs, in which observable morphological
changes can be identified. Referring also to YOHKOH observations,
H. Hudson discussed an important new coronal feature associated with
a CME: a dimming of the corona. If this effect can be substantiated
it will certainly represent a key factor for forecasting geomagnetic
storms associated with CMEs, although critical information about the
origin of a substantial southward (perpendicular to the ecliptic)
component of the IMF, necessary for the growth of storms, will still
need to be added toward a more precise forecasting. With respect to
the origin of intense geomagnetic storms, Gonzalez et al. presented
evidence about combined solar structures of the "coronal hole-active
region-current sheet" (CHARCS for short) type, as being candidates
for the origin of intense storms, especially when the associated
coronal hole grows in size rapidly near the active region-current
sheet structures.

With respect to the solar-interplanetary coupling, J. Chen summarized
several theoretical and observational aspects of the CME/prominence
association and of the solar ejecta's transport in the interplanetary
medium as a magnetic cloud structure. Toward the interest of
forecasting geomagnetic storms, B. V. Jackson summarized heliospheric-
remote sensing observations using ground and satellite techniques,
both for transient as well as for corotating solar-interplanetary
features.

Concerning the interplanetary structures that cause magnetic storms,
C. F. Farrugia summarized our present understanding about magnetic
clouds, whereas B. T. Tsurutani and W. D. Gonzalez reviewed other
structures which also involve large-amplitude and long-duration Bs
fields, mainly of the "sheath" field type. These two complementary
presentations focused also on the currently unsolved problems about
the interplanetary origin of storms. In addition to those two
presentations, D. Odstrcil presented a 3-dimensional, time-dependent
MHD numerical model to investigate the interaction between magnetic
clouds and the heliospheric current sheet, which could lead to an
additional source of Bs structures and consequently to the development
of storms.

MAGNETOSPHERIC PROCESSES. The above mentioned interplanetary
structures involving substantial Bs fields are expected to effectively
transfer energy to the magnetosphere which, after being stored mainly
in the tail, gets channeled to the inner magnetosphere. Among the
magnetospheric processes that signal the occurrence of storms, it has
been classically accepted that the most accepted one is the
intensification of the ring current. Thus, in this Conference some
reviews and contributed papers have dealt with such basic
magnetospheric processes as a general background for the understanding
of storm dynamics. V. M. Vasyliunas presented an overview of the
global energetics of the magnetosphere during magnetic storms,
starting with the solar wind MHD dynamo concept and following with
general concepts about energy storage and dissipation processes in
the magnetosphere. Toward a more quantitative understanding of those
processes, R. A. Wolf presented an updated overview of the Rice
convection model as applied to the understanding of magnetic storms,
including the relationship between time-dependent convection and
diffusion. For completeness, S. Kokubun presented a summary of our
present knowledge about the dynamic behavior of the distant magnetotail
during magnetic storms, using GEOTAIL and ISEE-3 data. Three additional
contributions dealt with the tail behavior during storms. W. Baumjohann
et al. presented data from the IRM satellite in the near magnetotail
to discuss tail signatures during isolated substorms as compared to
intervals with substorms occurring within storm events. They concluded
that not all substorms are alike and that the near-earth neutral line
scenario may apply only to the storm-time substorms. L. Frank presented
plasma velocity distributions obtained from GEOTAIL measurements also
at the near-earth magnetotail, showing that during storm intervals
there are clear field-aligned electron beams and field-aligned beams
of singly charged oxygen ions flowing from the ionosphere. On the
other hand, C. M. Ho and B. T. Tsurutani, using ISEE-3 data collected
at the distant magnetotail, presented evidence of strong earthward
flowing events probably originated at distances beyond ISEE-3. It is
not thought that such distant tail reconnection/jetting is important
for near-Earth substorms, however. Such events are probably associated
with additional flux sloughing.

The issue of magnetospheric energization and its dissipation in storms
and substorms was discussed by R. M. MacMahon et al. They presented
results associated with superstorms, for which it was found that about
1% of the energy transferred by the solar wind to the magnetosphere
is used to build up the ring current.

STORM DYNAMICS The topic of storm dynamics, involving ring current
evolution and population as well as the issue of storm/substorm
relationship(s), was certainly one of the hottest and busiest in this
Conference. I. A. Daglis, while discussing the role of magnetosphere-
ionosphere coupling in storm dynamics, raised the very interesting
issue of the role of the ionosphere in ring current population and
evolution. He presented evidence from the CRRES and AMPTE/CCE
spacecraft about the dominance of oxygen ions over the other ring
current constituents during the main phase of intense storms. D. C.
Hamilton added more evidence to these findings by also contrasting the
ring current population during the maximum and minimum phases of the
solar cycle. Further, M. Grande complemented these talks with a review
about ring current composition contrasting the solar wind material
and the ionospheric one as competitive sources. He also raised the
subject of the difference between substorms during storm times and
quiet times.

Modeling ring current formation and decay is a key subset of storm
research. This was addressed by M. W. Chen et al., who reviewed our
present understanding of the transport and loss processes, involving
large-scale electric and magnetic field variations, wave generation
and convection versus diffusion processes under both quiescent and
storm-time conditions. This talk was complemented by another review
given by J. V. Kozyra et al. about the role of electromagnetic ion
cyclotron (EMIC) waves in storm-time ring current erosion. On the
other hand, L. M. Kistler concentrated on the pitch angle distributions
of ring current ions during the main phases of storms, showing
statistical results of the distributions of four major species, namely
H+, O+, He+ and He++.

Dealing with the evolution of the storm-ring current, A. L. Clua de
Gonzalez et al. examined the energy balance equation in order to
understand the role of the energy input variability, as governed by
the solar wind. Some analytic solutions for Dst variations were found
for simple solar wind governing structures.

Two interesting presentations also addressed the role of electric
fields in the energization of ring current and radiation belt particles.
J. R. Wygant, using electric field observations from CRRES during major
magnetic storms, showed clear associations between intense convection
electric fields and large changes in the ring current injection rate,
as well as between intense fluctuations in the electric field (with
large power) and abrupt appearance of trapped radiation belt-electron
population. To complement this, M K. Hudson et al. presented results
from MHD simulations of the radiation belt formation during storm
sudden commencements.

Among new experimental projects which are expected to help us to better
understand the processes associated with ring current formation and
decay, G. Haerendel reviewed the instrumentation and scientific goals
of the EQUATOR-S satellite, expected to be launched in early 1997.

The very important issue of storm/substorm relationship was reviewed
by R. L. McPherron and by G. Rostoker. They presented complementary
talks showing that the ring current is mainly controlled by changes
in the interplanetary electric field variability and that substorms,
despite the fact that they occur more intensively and frequently during
the storm's main phase, may not play an important role in ring current
development. However, the final (panel) session of the Conference
considered this issue as one deserving further future studies (in
fact, a small workshop was held at Lake Arrowhead, California, right
after the Conference, to discuss this matter).

Showing in fact that the topic of storm/substorm relationship is still
largely open for more research, I. V. A. Sergeev discussed about steady
magnetospheric convection events involving strong recurrent substorms
and near-earth cross tail intensified currents, whereas Y. I. Feldstein
and A. Grafe dealt with latitudinal and intensity changes of auroral
electrojets and of the ionospheric role in ring current development.

THERMOSPHERIC, IONOSPHERIC AND GROUND EFFECTS - STORM FORECASTING.
The thermospheric and ionospheric effects of storms are observationally
an old field of research. However the processes which are involved are
even at present not fully understood. Nevertheless, an excellent review
about some of the key processes was given by G. W. Proelss, who
concentrated on the large scale morphology and the physical processes
associated with magnetic storm perturbations in the upper atmosphere. He
also focused on the large-scale wind circulation at several latitudinal
regions and on the associated compositional changes. In a complementary
effort, T. Fuller-Rowell reviewed the present status of modeling the
thermospheric response to magnetic storms, including the "positive" and
"negative" ionospheric responses and their seasonal and local time
variability. He also presented a summary of the sources for ionospheric
and thermospheric perturbations at low latitudes, although a more
detailed description of this subject, especially in terms of electric
fields, was given by B. G. Fejer and L. Scherliess. Further, J. H. A.
Sobral et al. discussed this same topic as applied to intervals with
intense storms.

On the other hand Szuszczewicz et al. presented an overview of storm-
time characteristics of the global ionospheric-thermospheric system
using a global network of observations carried during several
observational campaigns, in an effort that exemplifies several of the
points reviewed by the previous speakers.

Two other talks focused on detailed aspects of ionospheric and
thermospheric response to storms during particular events. B. A. Emery
et al. presented the results of such a study for the storm of March
28-29, 1992, as well as the related TIGCM/AMIE simulations. D. J.
Knipp presented the results of a similar collaborative study for the
storm of November 3-4, 1993, including complementary observations at
the sun, the interplanetary medium and the magnetosphere, as collected
through the CEDAR and GEM campaigns.

W. H. Campbell reviewed several aspects related to what he called a
"societal impact of geomagnetic storms", including satellite damage
and tracking, induction in long pipelines and electric power grids,
communication and global positioning systems as well as association
of geomagnetism with weather and life forms. The issue of geomagnetic
effects on power systems were further discussed by D. H. Boteler and
by J. G. Kappenman and W. A. Radasky, who described also the need of
further research in this field towards a better protection of the
electric utility industry, including delicate situations such as
nuclear power plants.

Finally, with regard to the important goal of geomagnetic storm
forecasting, several presentations raised complementary aspects of
this problem. H. Lundstedt, reviewed AI methods used in long, medium
and short-term predictions of geomagnetic storms, using solar and
solar wind data. He stressed the importance of using more advanced
neural networks and hybrids of different AI-methods, which together
with new observations can improve the accuracy of storm forecasting.

T. R. Detman and D. Vassiliadis tried on the other hand to review
different approaches of storm forecasting using linear and non-linear
techniques in order to be able to obtain short term predictions for
the geomagnetic indices as well as medium and longer term predictions
of storms. For the latter case they discussed the importance of
improving present heliospheric and magnetospheric models as well as
remote sensing techniques of solar and interplanetary processes.

Other talks on storm forecasting helped to visualize more the present
problems for improving our forecasting ability. A. S. Sharma et al.
discussed non-linear dynamic models involving phase space reconstruction
techniques that allow quantitative predictions of the level of storm
development as a function of solar wind data. J. Chen et al. discussed
another approach to forecast storms, following the evolution of physical
features of interplanetary structures rather than a simple time-series
information. This approach is expected to help us better understand
also the physical processes associated with the solar wind-magnetosphere
interaction. On the other hand, S. Bravo focused on the difficult
problem of long-term storm forecasting using soft x- ray imaging of
coronal transients and the tracking of solar wind disturbances by
means of interplanetary scintillations.

The Conference was closed by a Panel Discussion, chaired by Y. Kamide
and R. McPherron, in which S. W. Kahler, H. Hudson, W. D. Gonzalez,
D. C. Hamilton, L. R. Lyons, E. P. Szuszczewicz, H. H. Lundstedt and
J. A. Joselyn highlighted some of the main conclusions and also
presented open questions for future research. The AGU Monograph (with
the review papers of this conference) will contain also a chapter about
this Panel Discussion.

This summary was contributed by the Convenors of the Conference: W.
D. Gonzalez (INPE - Brazil), Y. Kamide (STEL - Japan), and B. T.
Tsurutani (Jet Propulsion Laboratory, Pasadena).