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We use magnetic field and plasma observations from the Van Allen Probes,\udTime History of Events and Macroscale Interactions during Substorms (THEMIS) and Geostationary Operational Environmental Satellite system (GOES) spacecraft to study the spatial and temporal characteristics\udof long-lasting poloidal Pc4 pulsations in the dayside magnetosphere. The\udpulsations were observed after the main phase of a moderate storm during low\udgeomagnetic activity. The pulsations occurred during various interplanetary\udconditions and the solar wind parameters do not seem to control the\udoccurrence of the pulsations. The most striking feature of the Pc4 magnetic\udfield pulsations was their occurrence at similar locations during three of\udfour successive orbits. We used this information to study the latitudinal\udnodal structure of the pulsations and demonstrated that the latitudinal\udextent of the magnetic field pulsations did not exceed 2 Earth radii\ud(RE). A phase shift between the azimuthal and radial components of the\udelectric and magnetic fields was observed from ZSM  =  0.30 RE to ZSM  =  −0.16 RE. We used magnetic and electric field data from Van Allen\udProbes to determine the structure of ULF waves. We showed that the Pc4\udmagnetic field pulsations were radially polarized and are the second-mode harmonic waves. We suggest that the spacecraft were near a magnetic field\udnull during the second orbit when they failed to observe the magnetic field\udpulsations at the local times where pulsations were observed on previous and\udsuccessive orbits. We investigated the spectral structure of the Pc4\udpulsations. Each spacecraft observed a decrease of the dominant period as it\udmoved to a smaller L shell (stronger magnetic field strength). We demonstrated\udthat higher frequencies occurred at times and locations where Alfvén\udvelocities were greater, i.e., on Orbit 1. There is some evidence that the\udperiods of the pulsations increased during the plasmasphere refilling\udfollowing the storm

Multipoint spacecraft observations of long-lasting poloidal Pc4 pulsations in the dayside magnetosphere on 1–2 May 2014