The Equator-S mission     

G. Haerendel  R. B. Torbert  H. Höfner 《Annales Geophysicae》1999,17(12):1499-1502

In spite of its short operational life of only five months, the major goals of the Equator-S mission were fulfilled, except that its contribution to the ISTP science is restricted to the morning sector of the outer magnetosphere. A set of twelve papers following this introduction is a first documentation of the achievements. They span from the successful testing and operation of the most advanced and complex way of measuring electric fields in a hot plasma environment by means of electron beams, to various investigations at or near the equatorial magnetopause and in the plasma sheet.  相似文献   

Deep Solar Activity Minimum 2007 – 2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere     

Farrugia  C. J.  Harris  B.  Leitner  M.  Möstl  C.  Galvin  A. B.  Simunac  K. D. C.  Torbert  R. B.  Temmer  M. B.  Veronig  A. M.  Erkaev  N. V.  Szabo  A.  Ogilvie  K. W.  Luhmann  J. G.  Osherovich  V. A. 《Solar physics》2012,281(1):461-489

We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007?–?2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfvén Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind–magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from Wind and ground-based observations: i) the dayside contribution to the cross-polar cap potential (CPCP), and ii) the shapes of the magnetopause and bow shock. For i) we find a low interplanetary electric field of 1.3±0.9 mV?m^?1 and a CPCP of 37.3±20.2 kV. The auroral activity is closely correlated to the prevalent stream–stream interactions. We suggest that the Alfvén wave trains in the fast streams and Kelvin–Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For ii) we determine 328 magnetopause and 271 bow shock crossings made by Geotail, Cluster 1, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey. We use the same numerical approach as in Fairfield’s (J. Geophys. Res. 76, 7600, 1971) empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 R _E and 14.35 R _E, respectively. When comparing with Fairfield’s (1971) classic result, we find that the subsolar magnetosheath is thinner by ～1 R _E. This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause. The magnetopause is more flared than in Fairfield’s model. By contrast the bow shock is less flared, and the latter is the result of weaker MHD forces.

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EDI electron time-of-flight measurements on Equator-S     

G. Paschmann  N. Sckopke  H. Vaith  J. M. Quinn  O. H. Bauer  W. Baumjohann  W. Fillius  G. Haerendel  S. S. Kerr  C. A. Kletzing  K. Lynch  C. E. McIlwain  R. B. Torbert  E. C. Whipple 《Annales Geophysicae》1999,17(12):1513-1520

We present the first electron time-of-flight measurements obtained with the Electron Drift Instrument (EDI) on Equator-S. These measurements are made possible by amplitude-modulation and coding of the emitted electron beams and correlation with the signal from the returning electrons. The purpose of the time-of-flight measurements is twofold. First, they provide the drift velocity, and thus the electric field, when the distance the electrons drift in a gyro period becomes sufficiently large. Second, they provide the gyro time of the electrons emitted by the instrument, and thus the magnitude of the ambient magnetic field, allowing in-flight calibration of the flux-gate magnetometer with high precision. Results of both applications are discussed.  相似文献   

EDI convection measurements at 5–6 RE in the post-midnight region     

J. M. Quinn  G. Paschmann  N. Sckopke  V. K. Jordanova  H. Vaith  O. H. Bauer  W. Baumjohann  W. Fillius  G. Haerendel  S. S. Kerr  C. A. Kletzing  K. Lynch  C. E. McIlwain  R. B. Torbert  E. C. Whipple 《Annales Geophysicae》1999,17(12):1503-1512

We present the first triangulation measurements of electric fields with the electron drift instrument (EDI) on Equator-S. We show results from five high-data-rate passes of the satellite through the near-midnight equatorial region, at geocentric distances of approximately 5–6 R_E, during geomagnetically quiet conditions. In a co-rotating frame of reference, the measured electric fields have magnitudes of a few tenths of mV/m, with the E × B drift generally directed sunward but with large variations. Temporal variations of the electric field on time scales of several seconds to minutes are large compared to the average magnitude. Comparisons of the “DC” baseline of the EDI-measured electric fields with the mapped Weimer ionospheric model and the Rowland and Wygant CRRES measurements yield reasonable agreement.  相似文献