CXO Project Science: Coronal Mass Ejection of 2000 Apr 04

This page documents the response of the solar wind and magnetosphere to a coronal mass ejection at 2000 Apr 04 (D095) 15 GMT. The contemporaneous real-time data plots are from the NOAA Space Environment Center, using data from NASA's Advanced Composition Explorer (ACE), in L1 orbit, and from NOAA's Geostationary Operational Environmental Satellites (GOES).

ACE Solar Isotope Spectrometer (SIS) shows a rapid increase in the high-energy (> 10 MeV) proton flux, at Apr 04 (D095) 16 GMT, representing the vanguard of the Solar Energetic Particles (SEP) generated in the CME.

ACE Electron, Proton, and Alpha Monitor (EPAM) shows a rapid increase in the electron flux, at Apr 04 (D095) 16 GMT, representing the vanguard of the Solar Energetic Particles (SEP) generated in the CME. The proton flux increases most rapidly at the higher energies, as the SEPs diffuse supersonically into the solar wind. Then, at Apr 06 (D097) 16 GMT, the proton flux in all EPAM channels suddenly increases, as a solar-wind shock front passes ACE.

ACE MAGnetometer instrument (MAG) and ACE Solar-Wind Electron, Proton, and Alpha Monitor (SWEPAM) show the passing of a pronounced solar-wind shock front at Apr 06 (D097) 16 GMT. At this time, SWEPAM reports the solar-wind speed suddenly increasing from under 400 km/s to over 600 km/s, and the density and temperature also increasing; about an hour later, MAG reports a rapid change in Bz from about 0 to -20 nT.

NOAA SEC's Satellite Environment Plot, based on GOES MAGnetometer (MAG) and Energetic Particle Sensor (EPS) data and on ground-based data, show the induced magnetospheric disturbance as the solar-wind shock passes the Earth (1.5 million km downstream from ACE, at L1) at Apr 06 (D097) 17 GMT. The planetary K index (Kp) reaches 8, indicating a "Severe" (G4) geomagnetic storm on NOAA's Space Weather Scale.

The quick-look Disturbance Storm Time (Dst) index for 2000 Apr, generated by the World Data Center for Geomagnetism (Kyoto), shows the effects, starting at Apr 06 (D097) 19 GMT, of the post-shock high-ram pressure and negative Bz upon ground-based measurements of the equatorial magnetic field. The estimated Dst drops below -300 nT, indicating a significant injection of ring current, in about 5 hours and then recovers over the next day or so.

The quick-look Auroral Electrojet (AE) index for 2000 Apr 06, generated by the World Data Center for Geomagnetism (Kyoto), shows the effects, starting at Apr 06 (D097) 17 GMT, of the post-shock high-ram pressure and negative Bz upon ground-based measurements of the auroral-latitude magnetic field. The estimated AE range builds to -600 to +2000 nT in about an hour, then recovers over the few hours.

Dynamic modeling (S. M. Petrinec) of Earth's bow shock and magnetopause, using the ACE MAG/SWEPAM data, simulates the response of the bow shock and magnetopause on Apr 06. The 5 animated GIFs by S. M. Petrinec show the post-shock increase in the solar-wind ram pressure and magnetic-field cancellation by the negative Bz driving the magnetopause inside geosynchronous orbit.

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