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"Space Weather: Myths and reality"

Yu. I. Yermolaev, M. Yu. Yermolaev, G. N. Zastenker, L. M. Zelenyi, A. A. Petrukovich (IKI) 

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 () - cover only small part of a researched interval. However available observations show, that in half of cases result in medium storms with -100 n < Dst <-60 n and in 2/3 cases in strong storm with Dst <-100 n.

The most geoeffective interplanetary phenomena are magnetic clouds () which, as many believe, are interplanetary manifestations of , and compressions in the region of interaction of slow and fast streams in the solar wind (corotating interaction region, CIR).  Phenomena and CIR are  accompanied by about all 2/3 observed magnetic storms, and for storms with Dst <-60 n the amounts of and CIR are approximately identical, and for strong storms with Dst <-100 n the number of storms from 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 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 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 IKIs suggestions on research of questions of Space Weather in the INTERBALL-PROGNOZ (INTERBALL-3) project are discussed.