TY - JOUR
T1 - On the association of quiet-time Pi2 pulsations with IMF variations
AU - Cheng, Ching Chang
AU - Russell, Christopher T.
AU - Shue, Jih Hong
N1 - Funding Information:
The IGPP/LANL and SMALL data archive was maintained by P.J. Chi. The propagated solar wind data of the Wind spacecraft were provided by J. Weygand. The GOES 8, GOES 9, and GOES 10 magnetic field data were provided by H. Singer at NOAA via CDAWeb. The magnetic field and LEP data at Geotail were respectively, provided by S. Kokubun and T. Mukai at ISAS in Japan via CDAWeb. The magnetic field and proton flux data at Interball were provided by S. Romanov at SRI in Russia via CDAWeb. We thank G. Parks for use of the Polar UVI images. This work was supported by National Science Council of R.O.C. on Taiwan under the Grant NSC 96-2111-M-150-001, and by National Space Organization under the Grant 96- NSPO(B)-SP-FA07-01(A). The work at UCLA was supported by the U.S. National Science Foundation under research Grant ATM04-02213.
PY - 2009/4/1
Y1 - 2009/4/1
N2 - The association of quiet-time Pi2 pulsations with the variations of the interplanetary magnetic field (IMF) has been examined by using three reported events, occurring during extremely quiet intervals, of which the first was on 10 March 1997, the second 27 December 1997, and the third 11 May 1999. For the first event, the onset time of ground Pi2s maps to the IMF structure bearing a variation cycle of north-to-south and north again as seen by Wind in the upstream region and Geotail in the magnetosheath. Likewise, the second and the third events have respectively, four and three recurrent turnings propagating to the Earth sensed by multiple satellites. The comparison of geomagnetic perturbations, auroral brightenings, and energetic particle data in the magnetotail with the IMF observations shows successive substorm-like activations accompanied by ground Pi2 onsets. For a clear variation cycle, the first Pi2 burst appears 36 ± 8 min after southward turning of the IMF and the second one follows14 ± 4 min after a northward turning. Moreover, ground Pi2 onsets recur under low IMF clock angle conditions. These observational results can be interpreted with the prevailing models of externally triggered substorm. But the solar wind coupling to the magnetosphere under quiet conditions proceeds in a less efficient way than under substorm time conditions. Consequently, we suggest that recurrent quiet-time Pi2s can be associated with IMF variations and their cause can be the same as those for substorm times.
AB - The association of quiet-time Pi2 pulsations with the variations of the interplanetary magnetic field (IMF) has been examined by using three reported events, occurring during extremely quiet intervals, of which the first was on 10 March 1997, the second 27 December 1997, and the third 11 May 1999. For the first event, the onset time of ground Pi2s maps to the IMF structure bearing a variation cycle of north-to-south and north again as seen by Wind in the upstream region and Geotail in the magnetosheath. Likewise, the second and the third events have respectively, four and three recurrent turnings propagating to the Earth sensed by multiple satellites. The comparison of geomagnetic perturbations, auroral brightenings, and energetic particle data in the magnetotail with the IMF observations shows successive substorm-like activations accompanied by ground Pi2 onsets. For a clear variation cycle, the first Pi2 burst appears 36 ± 8 min after southward turning of the IMF and the second one follows14 ± 4 min after a northward turning. Moreover, ground Pi2 onsets recur under low IMF clock angle conditions. These observational results can be interpreted with the prevailing models of externally triggered substorm. But the solar wind coupling to the magnetosphere under quiet conditions proceeds in a less efficient way than under substorm time conditions. Consequently, we suggest that recurrent quiet-time Pi2s can be associated with IMF variations and their cause can be the same as those for substorm times.
KW - Auroral brightenings
KW - Clock angle
KW - IMF variations
KW - Northward turning
KW - Pi2 pulsations
KW - Substorm
UR - http://www.scopus.com/inward/record.url?scp=61449144382&partnerID=8YFLogxK
U2 - 10.1016/j.asr.2008.12.001
DO - 10.1016/j.asr.2008.12.001
M3 - 期刊論文
AN - SCOPUS:61449144382
SN - 0273-1177
VL - 43
SP - 1118
EP - 1129
JO - Advances in Space Research
JF - Advances in Space Research
IS - 7
ER -