Jordanova, V. K.,
Co-Authors: C. J. Farrugia, J. F. Fennell, and J. D. Scudder,
Title: An evaluation of the Ring, Magnetopause, and tail currents on the day the solar wind almost disappeared,
Reference: J. Geophys. Res., 106, 25529, 2001.
Reference Type: Published Journal
CEPPAD: true
CAMMICE: true
RAPID: false
Abstract:
We study ring current dynamics on a day of exceptionally low solar wind density (less than 0.1 cm–3). Inner magnetospheric measurements of geomagnetic activity show geomagnetic quiet par excellence. On May 11, 1999, the values were |Dst| < 10 nT and Kp =0 + . The field at geostationary orbit was very close to dipolar. We simulate the global evolution of the ring current during this period and compare the relative sizes of the magnetopause, ring, magnetotail and field-aligned currents. Measured H + , He + , and O + energy and pitch angle distributions by the MICS and HYDRA instruments on Polar on May 9 are used as initial conditions for our kinetic model. Comparing model results with Polar data on May 11, we find remarkable agreement, proving the applicability of our model for these magnetospheric conditions. We compare modeled H + and He + ion distributions with quiet-time ring current distributions inferred from statistical studies and find that, as a general tre! nd, the simulation results have lower values than the statistical patterns. The strengths of the ring and the magnetopause currents decrease quasi-monotonically on May 11, reaching limiting magnitudes of ~5 and ~3 nT, respectively. These values are smaller than the ~20 nT quiet-time values inferred from statistical studies.
