Abstract
Multi‐instrument observations of a Pg pulsation, which occurred on the morning of May 16, 1998, are reported. The wave signature was observed simultaneously on the ground, by the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network and in the ionosphere by the Doppler Pulsation Experiment (DOPE) high resolution HF Doppler sounder. The wave occurred in the morning sector and possessed an azimuthal wave number, m, of 30±5 with a westward phase propagation. Shortly before the Pg commenced, energetic particle instruments on board the Polar spacecraft detected protons with a non‐Maxwellian energy distribution drifting westward toward the location of IMAGE and DOPE. An investigation has been undertaken to determine whether these particles were involved in the wave‐particle interaction considered responsible for generating the Pg pulsation. Proton energies of around 7 keV, which occur at the low‐energy edge of the unstable distribution (where ∂ƒ/∂W>0), satisfy the drift‐bounce resonance relation, ω − mωd, for N=1. This result indicates that this particular wave is likely to be the result of a drift‐bounce resonance mechanism and that it has an even mode standing wave structure in the magnetosphere. This result is discussed in terms of previous observations of Pgs.
Highlights
Multi-instrumentobservationosf a Pg pulsationw, hichoccurredonthemorningof May 16, 1998,arereported.The wavesignaturewasobservedsimultaneousloynthe ground,by theInternationaMl onitor for AuroralGeomagneticEffects(IMAGE) magnetometenr etwork andin theionospherbey theDopplerPulsationExperiment(DOPE) highresolutionHF Doppler sounderT. hewave occurredin themorningsectorandpossesseadn azimuthalwavenumber,m, of 30+5 with a westwardphasepropagationS. hortlybeforethePg commencede, nergetic particleinstrumentosnboardthePolarspacecrafdt etectedprotonswith a non-Maxwellian energydistributiondriftingwestwardtowardthelocationof IMAGE andDOPE
Explaintheir results.The commentby Mann and Chisham[2000] The Doppler Pulsation Experiment (DOPE) sounder makes routine HF continuous wave which followed suggestedthat if the real "bump-on-the-tail" soundingsof the ionosphereoverTromsowith high spatialand responsiblewas outsideof the energyrangeof the distribution temporalresolution.The temporalresolutionof the DOPE data presented by Glassmeieret al. [1999] the resonance presentedhere is 12.8 s
This paperpresentsa studyof a Pg pulsationwhich occurred km), it is clear that a Doppler sounder offers ionospheric on the morningof May 16, 1998.It wasinitially identifiedby the observations with high spatial resolution
Summary
1982;Kokubunetal., 1989;Takahasheit al., 1992;Glassmeieert al., 1999],VHF aurorarladars[Poulteer t al., 1983;Chishamet. Integervalue of N andinsteadmodifiedthis conditionin orderto theintervalreportedhere,thesoundefrrequencywas4.45 MHz. explaintheir results.The commentby Mann and Chisham[2000] The DOPE sounder makes routine HF continuous wave which followed suggestedthat if the real "bump-on-the-tail" soundingsof the ionosphereoverTromsowith high spatialand responsiblewas outsideof the energyrangeof the distribution temporalresolution.The temporalresolutionof the DOPE data presented by Glassmeieret al. When comparedto the scale size of the significantly larger energy range than those presented by integrationarea of groundmagnetometers(>120 km) [Hughes This paperpresentsa studyof a Pg pulsationwhich occurred km), it is clear that a Doppler sounder offers ionospheric on the morningof May 16, 1998.It wasinitially identifiedby the observations with high spatial resolution.
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