William F. Denig

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During the March 20-22, 1990, magnetic storm, Millstone Hill radar and DMSP satellite observations detailed the conditions surrounding the occurrence ofa SAR arc which was observed continuously through an 8-hour interval from dusk till past midnight in the North American sector. All-sky imaging with a 630.0-nm imager continually monitored the(More)
The Cluster spacecraft experienced several boundary layer encounters when flying outbound from the magnetosphere to the magnetosheath in the dusk sector on 14 January 2001. The dayside boundary layer was populated by magnetosheath electrons, but not with quite as high densities as in the magnetosheath itself. The Cluster ground track was calculated using(More)
Although listed as one of the most significant events of the last 80 years, the space weather storm of late May 1967 has been of mostly fading academic interest. The storm made its initial mark with a colossal solar radio burst causing radio interference at frequencies between 0.01 and 9.0 GHz and near-simultaneous disruptions of dayside radio communication(More)
The focus of the study is a region of enhanced ionospheric densities observed by the EISCAT Svalbard radar in the polar F-region near local magnetic noon under conditions of IMF Bz<0. Multi-instrument observations, using optical, spacecraft and radar instrumentation, together with radio tomographic imaging, have been used to identify the source of the(More)
In this paper we focus on flux transfer events (FTEs) and poleward moving auroral forms (PMAFs) in the cusp region, combining data from the EISCAT Svalbard radar, SuperDARN HF radars, ground-based optics, and three low-altitude polar-orbiting spacecraft. During an interval of southward interplanetary magnetic field the EISCAT Svalbard radar tracked a train(More)
Spatial structures in ionospheric electron density revealed in a tomographic image have been identi®ed with auroral forms and related to their sources in precipitating particles observed by DMSP satellites. The observations of plasma enhancements relate to discrete auroral arcs seen in the post-noon sector, identi®ed by both redand green-line emissions(More)
In a case study we demonstrate the spatiotemporal structure of aurora and plasma convection in the cusp/polar cap when the interplanetary magnetic field (IMF) Bz < 0 and By ' |Bz| (clock angle in GSM Y − Z plane: ' 135). This IMF orientation elicited a response different from that corresponding to strongly northward and southward IMF. Our study of this(More)
In a case study, we investigate transitions between fundamental magnetosphere–ionosphere (M-I) coupling modes during storm-time conditions (SYM-H between −100 and−160 nT) driven by an interplanetary coronal mass ejection (ICME). We combine observations from the near tail, at geostationary altitude (GOES-10), and electrojet activities across the auroral oval(More)
On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ∼ 76) simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ∼ 16:00–18:00 MLT). The location of the auroras (near the ionospheric convection reversal boundary) and the clear correlation(More)