"Space Weather: Myths and reality"
Yu.
I.
Yermolaev, M.
Yu.
Yermolaev, G.
N.
Zastenker, L.
M.
Zelenyi, A.
A.
Petrukovich
Abstract:
Within
the framework of the " Space weather " program, 25-year sets of
observations of solar x-ray radiation, measurements of parameters of
plasma and a magnetic field in the solar wind and variations of Dst index
are analyzed with the purpose of revealing the factors rendering the
greatest influence on development magnetospheric storms.
Correlation
between strong solar flares and storms practically does not exceed a level
of correlation of random processes. .
In particular it was not found any dependence between importance of solar
flares and minimum of Dst index for storms which on time delay could be
connected to considered flares. The
data on the other type of solar activity - coronal mass ejection (СМЕ)
- cover only small part of a researched interval. However available
observations show, that СМЕ in half of cases result in medium storms
with -100 nТ < Dst <-60 nТ and in 2/3 cases in strong storm with
Dst <-100 nТ.
The
most geoeffective interplanetary phenomena are magnetic clouds (МС)
which, as many believe, are interplanetary manifestations
of СМЕ, and compressions
in the region of interaction of slow and fast streams in the solar wind (corotating
interaction region, CIR). Phenomena
МС and CIR are accompanied
by about all 2/3 observed magnetic storms, and for storms with Dst <-60
nТ the amounts of МС and CIR are approximately identical, and for
strong storms with Dst <-100 nТ the number of storms from МС is a
little bit higher. The analysis of behavior of solar wind plasma and
interplanetary magnetic field (IMF) parameters for geoeffective events in
the interplanetary space confirms the known fact, that the magnetosphere
is disturbed by events in which large negative (southward) component IMF
is observed long time. Just the similar situation is most frequently
registered in МС and CIR, that it is possible to explain to that if in
originally undisturbed solar wind there was southward component IMF there
is a compression and increase of all component IMF inside these phenomena
as a result of dynamic processes during МС and CIR passage.
In
the report the problems of reliability of geomagnetic disturbance
predictions are also in detail discussed on the basis of observations of
the Sun and monitoring of a condition in the interplanetary space.
Long-term (about day) forecasts are made on the basis of observation of
the Sun and now have low reliability (from 40 up to 70% on different
references) while short-term (about one hour) forecasts use measurements
of the interplanetary environment near to the Earth and show reliability
about 90-95%. So for example, on site Space Research Institute (IKI) http:
// www.iki.rssi.ru/apetruko/forecast/forecast.html there is a program
predicting the magnetic storms and substorms on the basis of real-time
measurements in parameters of solar wind and IMF on the ACE satellite
located in a libration point L1 between the Sun and the Earth on distance
1.5 million km from the Earth. Discrepancy (about 5%) of prediction of a
geomagnetospheric condition according to the far distant solar wind
monitor of ACE type is connected with two reasons: (1) In the limited
sizes and presence of inclined fronts in the structures of solar wind
which result in some cases in low correlation of the parameters measured
on the ACE and near the Earth on INTERBALL-1 satellite, and (2)
magnetosphere interaction not with the undisturbed solar wind, and with
the solar wind modified on the bow shock and in magnetosheath where the
large number of disturbances is observed, which are not directly connected
with parameter variations in the undisturbed solar wind.
Finally IKI's suggestions on research of questions of Space Weather in the INTERBALL-PROGNOZ (INTERBALL-3) project are discussed.