Vol 15, No 1

Effect of solar wind plasma parameters on space weather

Balveer S. Rathore, Dinesh C. Gupta, Subhash C. Kaushik


Abstract Today’s challenge for space weather research is to quantitatively predict the dynamics of the magnetosphere from measured solar wind and interplanetary magnetic field (IMF) conditions. Correlative studies between geomagnetic storms (GMSs) and the various interplanetary (IP) field/plasma parameters have been performed to search for the causes of geomagnetic activity and develop models for predicting the occurrence of GMSs, which are important for space weather predictions. We find a possible relation between GMSs and solar wind and IMF parameters in three different situations and also derived the linear relation for all parameters in three situations. On the basis of the present statistical study, we develop an empirical model. With the help of this model, we can predict all categories of GMSs. This model is based on the following fact: the total IMF Btotal can be used to trigger an alarm for GMSs, when sudden changes in total magnetic field Btotal occur. This is the first alarm condition for a storm’s arrival. It is observed in the present study that the southward Bz component of the IMF is an important factor for describing GMSs. A result of the paper is that the magnitude of Bz is maximum neither during the initial phase (at the instant of the IP shock) nor during the main phase (at the instant of Disturbance storm time (Dst) minimum). It is seen in this study that there is a time delay between the maximum value of southward Bz and the Dst minimum, and this time delay can be used in the prediction of the intensity of a magnetic storm two-three hours before the main phase of a GMS. A linear relation has been derived between the maximum value of the southward component of Bz and the Dst, which is Dst = (−0.06) + (7.65)Bz + t. Some auxiliary conditions should be fulfilled with this, for example the speed of the solar wind should, on average, be 350 km s−1 to 750 km s−1, plasma β should be low and, most importantly, plasma temperature should be low for intense storms. If the plasma temperature is less than 0.5 × 106 K then the Dst value will be greater than the predicted value of Dst or if temperature is greater than 0.5 × 106 K then the Dst value will be less (some nT).


Keywords solar wind — geomagnetic storms (GMSs) — interplanetary magnetic field (IMF)

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