A Technique of Forecasting Magnetic Field Properties of Interplanetary Coronal Mass Ejection

Sara F. Martin

Abtract

An experimental forecasting project was conducted during a 5 month interval during 1999. Quantitative forecasts of 4 properties of the magnetic fields of interplanetary coronal mass ejections (ICMEs) were made each time an erupting or disappearing filament was recognized from daily images of the Sun or observed in real time.  The properties were (1) sign of helicity, (2) direction of the axis in the front of the ICME assuming the form of a helical flux rope, (3)pitch angle of the flux rope, and (4) direction of the leading edge of the cloud excluding any initial draping field.  These forecasts are possible because of correlations of the chirality of ICMEs with the chirality of their source   coronal magnetic fields and filaments (Rust and Kumar 1994, Solar Phys. 155, 69) and evidence that ICMEs retain much of the original form of these source magnetic fields at the Sun (Marubashi 1997, Geophys Mono Serie 99, p 147). The primary objective in this forecasting project was to test the technique.  Most of the forecasts were issued 1-2 days after the eruptive event and before possible recording of the anticipated ICMEs in space.  A report of "no forecast" was made in this same time interval if there was insufficient chirality information immediatly available to make a forecast.  Of 232 erupting or disappearing filaments during the 5 month interval, forecasts were made on 158 (68%).  The focus of the initial analyses is on approximately 20 major interplanetary events recorded by satellites during the forecasting project.

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