Telescopic and Microscopic Views of the Magnetosphere: Multispacecraft Observations
The magnetospheric research community has long sought the capability to view the Sun-Earth system in a global way and to probe concurrently the microphysical details of key physical regions. This objective has now been substantially realized with the combination of the CLUSTER and IMAGE missions. With the additional use of SOHO, ACE, FAST, SAMPEX, POLAR, and geostationary orbit spacecraft, there is a remarkable ability to apply both telescopic and microscopic principles. As an example, a bright active region on the Sun gave rise on 29 March 2001 to a fast halo coronal mass ejection (CME) event observed by SOHO instruments. Subsequently on 31 March, a strong interplanetary shock wave ahead of a magnetic cloud (probably arising from the earlier CME) passed the ACE spacecraft and hit the Earth’s magnetosphere. This driver compressed the subsolar magnetopause to ≤ 4 RE geocentric distance and initiated a powerful geomagnetic storm (minimum Dst ~ −360 nT). The CLUSTER set of four spacecraft were located in the midnight sector of the magnetosphere near perigee (r~4 RE) at ~0635 UT and observed a dispersionless injection of energetic (E ≥ 20 keV) electrons in association with a large magnetospheric substorm expansion phase onset (AE ~1200 nT). Concurrent to these in situ observations, the IMAGE spacecraft was returning a sequence of global Energetic Neutral Atom (ENA) images from the medium-energy (MENA) and high-energy (HENA) sensor systems. These data showed a very prominent injection of substorm ions in the premidnight (and postdusk) sector of the inner magnetosphere. This event is consistent with a substorm onset that pushed the substorm ‘injection boundary’ far inside of geostationary orbit and far toward the dusk sector. In another event on August 27, 2001, the IMAGE-CLUSTER combination provided evidence that magnetic reconnection began in the mid-tail plasma sheet some 7 min prior to auroral onset and brightening. Alternative interpretations may also be possible even with the multis-pacecraft data available. Notwithstanding, these data gave an unprecedented view both telescopically and microscopically of a magnetospheric substorm onset and help establish key process timing in the magnetosphere. Such available events reveal the power of multispacecraft observations.
KeywordsSolar Wind Magnetic Reconnection Plasma Sheet Geostationary Orbit Advance Composition Explorer
Unable to display preview. Download preview PDF.
- Baker, D.N. et al.: 2002a, ’A telescopic and microscopic view of a magnetospheric substorm on 31 March 2001’, Geophys. Res. Lett..Google Scholar
- Baker, D.N. et al.: 2002, ’Timing of magnetic reconnection initiation during a global magnetic substorm onset’, Geophys. Res. Lett, submitted.Google Scholar
- Balough, A. et al., ’The CLUSTER magnetic field investigation’, Space Sci Rev. 79, 65.Google Scholar
- Friedel, R.H.W, et al.: 1996, ’Substorm onsets observed by CRRES: Determination of energetic particle source regions’, J. Geophys. Res. 101, 13,137–13,154.Google Scholar
- Lyons, L.R.: 2000, ’Determinations of relative timing of near-Earth substorm onset and tail reconnection’, ESA SP-443, p. 255.Google Scholar
- Reeves, G.D. et al.: 1997, ’Los Alamos space weather data products: On line and on time, in Substorms 3’, ESA SP-339, 689–694.Google Scholar