Ring current activity during the early B-z < 0 phase of the January 1997 magnetic cloud

The passage at Earth of the January 10-11, 1997, magnetic cloud induced a s torm of moderate geomagnetic activity with Dst index reaching minimum value s of about -83 nT. We study ring current formation during-the early B-z neg ative phase of this magnetic cloud, using energetic particle data from thre e instruments on the Polar spacecraft and geosynchronous plasma data from t he LANL spacecraft. We use our kinetic drift-loss model to simulate the evo lution of ring current H+, He+, and O+ ion distributions and associated aer onomical effects during this period. The results from two Volland-Stern typ e magnetospheric electric field model formulations are compared: (1) Kp-dep endent and (2) interplanetary magnetic field (IMF) dependent. We demonstrat e that while both electric field models reproduce well the main trends of r ing current formation and decay during the storm, the IMF-dependent model r eproduces the rapidity of the main storm growth phase and its strength bett er. Comparing model results during the main phase of the storm with HYDRA, TIMAS, and CAMMICE data we find that the model reproduces very well the rin g current distributions near dawn. The formation of the nose event, i.e., t he rise of the 10-30 keV energy particles near dusk due to abruptly increas ed convection is, however, overestimated by the model. We compute plasmasph eric heating through Coulomb collisions as the storm evolves and find that maximum heating occurs initially on the nightside near L similar to 3.5 and subsequently moves earthward to L similar to 2.75: in agreement with Mills tone Hill radar observations of midlatitude electron temperature enhancemen t on January 10. However, the magnitude of the energy transferred to plasma spheric electrons through Coulomb collisions appears to be not sufficient t o yield the observed elevated electron temperature at similar to 0830 UT, s uggesting that additional energy sources should be considered during this e vent.