The geostationary field during dayside erosion events 1996-2001: A joint Wind, ACE, and GOES study

• Published in: Journal of Geophysical Research: Space Physics 2003-12, Vol.108 (A12), p.SMP4.1-n/a
• Main Authors: Mühlbachler, Stefan, Farrugia, Charles J., Biernat, Helfried K., Torbert, Roy B.
• Format: Article
• Language: English
• Subjects: Earth, ocean, space; erosion; Exact sciences and technology; External geophysics; magnetosphere; Physics of the high neutral atmosphere; Physics of the ionosphere; Physics of the magnetosphere
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2003JA009833

We carry out a statistical investigation on dayside magnetosphere erosion during the period 1996–2001, using Wind, ACE, and GOES observations supplemented by ground‐based magnetograms. The inner magnetospheric signature of erosion that we focus on is the depression of the geostationary magnetic field strength (ΔBtot) within 2 hours of local magnetic noon. We relate this decrease to the southward component of the interplanetary magnetic field (IMF) in the range −16 ≤ Bz ≲ 0 nT and the solar wind dynamic pressure in the range ∼0–6 nPa. Thus both relevant interplanetary parameters extend to well beyond average values at 1 AU. The geostationary field strength (Btot) is derived from measurements by the GOES 8, 9, and 10 spacecraft. Our data set consists of 288 measurements. We adopt two approaches. In one approach, we first correct for the effect of dynamic pressure on the geostationary field strength by studying days with various dynamic pressure values but low IMF clock angles, θ (