ULF wave activity during the 2003 Halloween superstorm: multipoint observations from CHAMP, Cluster and Geotail missions

摘要

We examine data from a topside ionosphere and two magnetospheric missions(CHAMP, Cluster and Geotail) for signatures of ultra low frequency (ULF) waves during theexceptional 2003 Halloween geospace magnetic storm, when Dst reached~−380 nT. We use a suite of wavelet-based algorithms, which are asubset of a tool that is being developed for the analysis of multi-instrumentmulti-satellite and ground-based observations to identify ULF waves andinvestigate their properties. Starting from the region of topside ionosphere,we first present three clear and strong signatures of Pc3 ULF wave activity(frequency 15–100 mHz) in CHAMP tracks. We then expand these three timeintervals for purposes of comparison between CHAMP, Cluster and Geotail Pc3observations but also to be able to search for Pc4–5 wave signatures(frequency 1–10 mHz) into Cluster and Geotail measurements in order to havea more complete picture of the ULF wave occurrence during the storm. Due tothe fast motion through field lines in a low Earth orbit (LEO) we are able toreliably detect Pc3 (but not Pc4–5) waves from CHAMP. This is the first time,to our knowledge, that ULF wave observations from a topside ionospheremission are compared to ULF wave observations from magnetospheric missions.Our study provides evidence for the occurrence of a number of prominent ULFwave events in the Pc3 and Pc4–5 bands during the storm and offers a platformto study the wave evolution from high altitudes to LEO. The ULF wave analysismethods presented here can be applied to observations from the upcoming Swarmmulti-satellite mission of ESA, which is anticipated to enable joint studieswith the Cluster mission.