Relationship between interplanetary field/plasma parameters with geomagnetic indices and their behavior during intense geomagnetic storms     

Navin Chandra Joshi  Neeraj Singh Bankoti  Seema Pande  Bimal Pande  Kavita Pandey 《New Astronomy》2011,16(6):366-385

This paper presents a correlative study between the peak values of geomagnetic activity indices (Dst, Kp, ap and AE) and the peak values of various interplanetary field (Bt, Bz, E and σ_B) and plasma (T, D, V, P and β) parameters along with their various products (BV, BzV and B²V) during intense geomagnetic storms (GMSs) for rising, maximum and decay phases as well as for complete solar cycle 23. The study leads to the conclusion that the peak values of different geomagnetic activity indices are in good correlation with Bt, Bz, σ_B, V, E, BV, BzV and B²V, therefore these parameters are most useful for predicting GMSs and substorms. These parameters are also reliable indicators of the strength of GMSs. We have also presented the lag/lead time analysis between the maximum of Dst and peak values of geomagnetic activity indices, various interplanetary field/plasma parameters for all GMSs. We have found that the average of peak values of geomagnetic activity indices and various field/plasma parameters are larger in decay phase compare to rising and maximum phases of cycle 23. Our analyses show that average values of lag/lead time lie in the ≈?4.00 h interval for Kp, ap and AE indices as well as for Bt, Bz, σ_B, E, D and P. For a more meaningful analysis we have also presented the above study for two different groups G1 (CME-driven GMSs) and G2 (CIR-driven GMSs) separately. Correlation coefficients between various interplanetary field/plasma parameters, their various products and geomagnetic activity indices for G1 and G2 groups show different nature. Three GMSs and associated solar sources observed during three different phases of this solar cycle have also been studied and it is found that GMSs are associated with large flares, halo CMEs and their active regions are close to the solar equator.  相似文献   

Equatorial electrojet in east Brazil longitudes     

R. G. Rastogi  H. Chandra  K. Yumuto 《Journal of Earth System Science》2010,119(4):497-505

This paper describes the morphology of the equatorial electrojet (EEJ) along 45°W longitude in east Brazil, where the ground magnetic (dip) equator is associated with the largest declination in the world. Daily range of the horizontal field (ΔH), as expected, was largest at the station in the chain closest to the dip equator, Sao Luiz (inclination −0.25°S). ΔZ was largest positive at Eusebio (inclination 9.34°S) and largest negative at Belem (inclination 7.06°N); both near the fringe of EEJ belt. ΔZ at Sao Luiz during the daytime was unexpectedly large negative in-spite of a small dip and also located south of the dip equator where ΔZ should be positive. Center of EEJ was found to be shifted southward of the dip equator by about 1° in latitude. During southern summer, ΔY started decreasing from 00 h and reached a minimum value in the afternoon, an abnormal feature not discussed for any station so far. The mid-day value of the direction of ΔH vector was 22°–24°W compared to the declination of 19°–21°W in the region.  相似文献