Grocott, A., Yeoman, T. K., Milan, S. E., Amm, O., Frey, H. U., Juusola, L., ...
Simultaneous observations by the Cluster spacecraft and SuperDARN radars are presented of magnetotail flux transport during northward, but BY-dominated IMF. Two events are discussed, which occurred...
Grocott, A., Yeoman, T. K., Milan, S. E., Amm, O., Frey, H. U., Juusola, L., ...
Simultaneous observations by the Cluster spacecraft and SuperDARN radars are presented of magnetotail flux transport during northward, but BY-dominated IMF. Two events are discussed, which occurred...
Grocott, A., Yeoman, T. K., Nakamura, R., Cowley, S. W. H., Frey, H. U., Rème, H., ...
On 07 September 2001 the Cluster spacecraft observed a "bursty bulk flow" event in the near-Earth central plasma sheet. This paper presents a detailed study of the coincident ground-based...
HF radar observations of high-aspect angle backscatter from the E-region (2008)
Milan, S. E., Lester, M., Yeoman, T. K., Robinson, T. R., Uspensky, M. V.
We present evidence for the observation of high-aspect angle HF radar backscatter from the auroral electrojets, and describe the spectral characteristics of these echoes. Such backscatter is observed...
Cusp structures: combining multi-spacecraft observations with ground-based observations (2008)
Trattner, K. J., Fuselier, S. A., Yeoman, T. K., Korth, A., Fraenz, M., Mouikis, C., ...
Recent simultaneous observations of cusp structures with Polar, FAST and Interball revealed remarkably similar features at spacecraft crossing the cusp. Such stable cusp structures could be observed...
Taylor, J. R., Cowley, S. W. H., Yeoman, T. K., Lester, M., Jones, T. B., Greenwald, R. A., ...
The response of the dayside ionospheric flow to a sharp change in the direction of the interplanetary magnetic field (IMF) measured by the WIND spacecraft from negative Bz and positive By, to...
Grocott, A., Yeoman, T. K., Nakamura, R., Cowley, S. W. H., Frey, H. U., Rème, H., ...
On 07 September 2001 the Cluster spacecraft observed a "bursty bulk flow" event in the near-Earth central plasma sheet. This paper presents a detailed study of the coincident ground-based...
HF radar observations of high-aspect angle backscatter from the E-region (2008)
Milan, S. E., Lester, M., Yeoman, T. K., Robinson, T. R., Uspensky, M. V.
We present evidence for the observation of high-aspect angle HF radar backscatter from the auroral electrojets, and describe the spectral characteristics of these echoes. Such backscatter is observed...
Cusp structures: combining multi-spacecraft observations with ground-based observations (2008)
Trattner, K. J., Fuselier, S. A., Yeoman, T. K., Korth, A., Fraenz, M., Mouikis, C., ...
Recent simultaneous observations of cusp structures with Polar, FAST and Interball revealed remarkably similar features at spacecraft crossing the cusp. Such stable cusp structures could be observed...
Taylor, J. R., Cowley, S. W. H., Yeoman, T. K., Lester, M., Jones, T. B., Greenwald, R. A., ...
The response of the dayside ionospheric flow to a sharp change in the direction of the interplanetary magnetic field (IMF) measured by the WIND spacecraft from negative Bz and positive By, to...
Dhillon, R. S., Robinson, T. R., Yeoman, T. K.
The Space Plasma Exploration by Active Radar (SPEAR) facility has successfully operated in the high-power heater and low-power radar modes and has returned its first results. The high-power results...
Modulation of radio frequency signals by ULF waves (2008)
Waters, C. L., Yeoman, T. K., Sciffer, M. D., Ponomarenko, P., Wright, D. M.
The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1?100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and...
Towards a synthesis of substorm electrodynamics: HF radar and auroral observations (2008)
Grocott, A., Lester, M., Parkinson, M. L., Yeoman, T. K., Dyson, P. L., Devlin, J. C., ...
At 08:35 UT on 21 November 2004, the onset of an interval of substorm activity was captured in the southern hemisphere by the Far UltraViolet (FUV) instrument on board the IMAGE spacecraft. This was...
Wilson, M. E., Yeoman, T. K., Baddeley, L. J., Kellet, B. J.
A statistical study is presented of the unstable proton populations, which contain the free energy required to drive small-scale poloidal mode ULF waves in the magnetosphere, observed at invariant...
Senior, A., Kosch, M. J., Yeoman, T. K., Rietveld, M. T., Mccrea, I. W.
Observations of HF radar backscatter from artificial field-aligned irregularities in an ionosphere perturbed by travelling disturbances due to atmospheric gravity waves are presented. Some features...
Dayside flow bursts and high-latitude reconnection when the IMF is strongly northward (2008)
Hu, H., Yeoman, T. K., Lester, M., Liu, R., Yang, H., Grocott, A.
The characteristics of dayside ionospheric convection are studied using Northern Hemispheric SuperDARN data and DMSP particle and flow observations when the interplanetary magnetic field (IMF) was...
Milan, S. E., Basu, S., Yeoman, T. K., Sheehan, R. E.
We examine the correspondence between high latitude ionospheric scintillation measurements made at 250MHz with the occurrence of 10MHz HF coherent radar backscatter, on 13 and 14 December 2002. We...
Wright, D. M., Davies, J. A., Yeoman, T. K., Robinson, T. R., Shergill, H.
The results of high latitude ionospheric modification experiments utilising the EISCAT heating facility at Tromsø are presented. As a result of the interaction between the high power pump waves and...
Robinson, T. R., Yeoman, T. K., Dhillon, R. S., Lester, M., Thomas, E. C., Thornhill, J. D., ...
Results are presented from the first two active experimental campaigns undertaken by the new SPEAR (Space Plasma Exploration by Active Radar) high-power system that has recently become operational on...
HF doppler sounder measurements of the ionospheric signatures of small scale ULF waves (2008)
Baddeley, L. J., Yeoman, T. K., Wright, D. M.
An HF Doppler sounder, DOPE (DOppler Pulsation Experiment) with three azimuthally-separated propagation paths is used to provide the first statistical examination of small scale-sized, high m waves...
Grocott, A., Yeoman, T. K., Milan, S. E., Cowley, S. W. H.
This paper presents the first interhemispheric radar observations interpreted as the ionospheric response to tail reconnection during IMF-northward non-substorm intervals. SuperDARN measurements of...
Baddeley, L. J., Yeoman, T. K., Wright, D. M., Trattner, K. J., Kellet, B. J.
The first statistical study of the unstable proton populations which contain "free energy" required to drive small-scale poloidal mode ULF waves in the magnetosphere between L-shell locations of 6...
Parkinson, M. L., Pinnock, M., Wild, J. A., Lester, M., Yeoman, T. K., Milan, S. E., ...
Earthward injections of energetic ions and electrons mark the onset of magnetospheric substorms. In the inner magnetosphere (L4), the energetic ions drift westward and the electrons eastward, thereby...
Multi-frequency HF radar measurements of artificial F-region field-aligned irregularities (2008)
Senior, A., Borisov, N. D., Kosch, M. J., Yeoman, T. K., Honary, F., Rietveld, M. T.
We present radar backscatter power measurements using the CUTLASS HF radar at Hankasalmi, Finland from F-region field-aligned irregularities induced by HF radio pumping with the EISCAT Heating...
Sinha, A. K., Yeoman, T. K., Wild, J. A., Wright, D. M., Cowley, S. W. H., Balogh, A.
The dynamic spectrum of ULF waves from magnetic field data obtained by the elliptically orbiting Cluster satellites (with an apogee of 119000km, perigee of 19000km and the orbital period of 57h) have...
Baddeley, L. J., Yeoman, T. K., Wright, D. M., Trattner, K. J., Kellet, B. J.
Many theories state that Ultra Low Frequency (ULF) waves with a high azimuthal wave number (m) have their energy source in wave-particle interactions, yet this assumption has been rarely tested...
Scoffield, H. C., Yeoman, T. K., Wright, D. M., Milan, S. E., Wright, A. N., Strangeway, R. J.
On 14 December 1999, a large-scale ULF wave event was observed by the Hankasalmi radar of the SuperDARN chain. Simultaneously, the FAST satellite passed through the Hankasalmi field-of-view,...
Mcwilliams, K. A., Sofko, G. J., Yeoman, T. K., Milan, S. E., Sibeck, D. G., Nagai, T., ...
An extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were monitoring the dayside magnetosphere and ionosphere between 14:00 and 18:00 UT on 18 January 1999. The...
A multi-instrument approach to mapping the global dayside merging rate (2008)
Provan, G., Yeoman, T. K., Lester, M., Milan, S. E.
For the first time three different methods have been used to calculate the global merging rate during the same substorm growth phase. The ionospheric plasma drift was monitored by six of the Northern...
Wright, D. M., Yeoman, T. K., Woodfield, E. E.
It is now a common practice to employ ground-based radars in an attempt to distinguish between those regions of the Earth's upper atmosphere which are magnetically conjugate to open and closed...
Grocott, A., Badman, S. V., Cowley, S. W. H., Yeoman, T. K., Cripps, P. J.
This paper further addresses the issue of nightside flow bursts which occur during intervals of northward but strongly BY-influenced IMF. Recent discussions of such bursts concerned intervals during...
Stereo CUTLASS - A new capability for the SuperDARN HF radars (2008)
Lester, M., Chapman, P. J., Cowley, S. W. H., Crooks, S. J., Davies, J. A., Hamadyk, P., ...
The Super Dual Auroral Radar Network (SuperDARN), which consists of networks of HF radars surrounding the northern and southern poles, has proven to be an extremely successful experimental technique...
Wright, D. M., Yeoman, T. K., Baddeley, L. J., Davies, J. A., Dhillon, R. S., Lester, M., ...
The EISCAT high power heating facility at Tromsø, northern Norway, has been utilised to generate artificial radar backscatter in the fields of view of the CUTLASS HF radars. It has been demonstrated...
SuperDARN radar HF propagation and absorption response to the substorm expansion phase (2008)
Gauld, J. K., Yeoman, T. K., Davies, J. A., Milan, S. E., Honary, F.
Coherent scatter HF ionospheric radar systems such as SuperDARN offer a powerful experimental technique for the investigation of the magnetospheric substorm. However, a common signature in the early...
Grocott, A., Cowley, S. W. H., Sigwarth, J. B., Watermann, J. F., Yeoman, T. K.
We present SuperDARN radar observations of the ionospheric flow during a well-observed high-latitude substorm which occurred during steady northward IMF conditions on 2 December 1999. These data...
Cash, S. R., Davies, J. A., Kolesnikova, E., Robinson, T. R., Wright, D. M., Yeoman, T. K., ...
A quantitative analysis is presented of the FAST satellite electric field and particle flux data during an EISCAT heating experiment run on 8 October 1998. Radio frequency heating, modulated at 3 Hz,...
Baddeley, L. J., Yeoman, T. K., Wright, D. M., Davies, J. A., Trattner, K. J., Roeder, J. L.
HF radar backscatter, which has been artificially-induced by a high power RF facility such as the EISCAT heater at Tromsø, has provided coherent radar ionospheric electric field data of...
Nightside studies of coherent HF Radar spectral width behaviour (2008)
Woodfield, E. E., Davies, J. A., Lester, M., Yeoman, T. K., Eglitis, P., Lockwood, M.
A previous case study found a relationship between high spectral width measured by the CUTLASS Finland HF radar and elevated electron temperatures observed by the EISCAT and ESR incoherent scatter...
Milan, S. E., Sato, N., Lester, M., Yeoman, T. K., Murata, Y., Doi, H., ...
Simultaneous all-sky camera and HF radar observations of the visual and E-region radar aurora in the west-ward electrojet suggest a close relationship between a pair of parallel east-west-aligned...
Davies, J. A., Yeoman, T. K., Rae, I. J., Milan, S. E., Lester, M., Lockwood, M., ...
Observations from the EISCAT VHF incoherent scatter radar system in northern Norway, during a run of the common programme CP-4, reveal a series of poleward-propagating F-region electron density...
Menk, F. W., Yeoman, T. K., Wright, D. M., Lester, M., Honary, F.
We report the simultaneous observation of 1.6?1.7 mHz pulsations in the ionospheric F-region with the CUTLASS bistatic HF radar and an HF Doppler sounder, on the ground with the IMAGE and SAMNET...
Milan, S. E., Lester, M., Yeoman, T. K.
Three intervals of polar patch formation, as observed by the CUTLASS Finland HF coherent radar, are presented. Simultaneous observations from a vertical ionosonde located at Longyearbyen on Svalbard,...
Mann, I. R., Voronkov, I., Dunlop, M., Donovan, E., Yeoman, T. K., Milling, D. K., ...
We present magnetospheric observations of very large amplitude global scale ULF waves, from 9 and 10 December 2000 when the upstream solar wind speed exceeded 600 km/s. We characterise these ULF...
Provan, G., Milan, S. E., Lester, M., Yeoman, T. K., Khan, H.
We perform a case study of a favourable conjunction of overpasses of the DMSP F11 and F13 spacecraft with the field of view of the Hankasalmi HF coherent scatter. At the time, pulsed ionospheric...
Wild, J. A., Cowley, S. W. H., Davies, J. A., Khan, H., Lester, M., Milan, S. E., ...
Cluster magnetic field data are studied during an outbound pass through the post-noon high-latitude magnetopause region on 14 February 2001. The onset of several minute perturbations in the...
Letter to the EditorA statistical study of the location and motion of the HF radar cusp (2008)
Yeoman, T. K., Hanlon, P. G., Mcwilliams, K. A.
The large-scale and continuous monitoring of the ionospheric cusp region offered by HF radars has been exploited in order to examine the statistical location and motion of the equatorward edge of the...
Provan, G., Yeoman, T. K., Milan, S. E., Ruohoniemi, J. M., Barnes, R.
The SuperDARN HF coherent scatter radars (Greenwald et al., 1995) provide line-of-sight (l-o-s) velocity measurements of ionospheric convection flow over the polar regions of the northern and...
Ionospheric cusp flows pulsed by solar wind Alfvén waves (2008)
Prikryl, P., Provan, G., Mcwilliams, K. A., Yeoman, T. K.
Pulsed ionospheric flows (PIFs) in the cusp foot-print have been observed by the SuperDARN radars with periods between a few minutes and several tens of minutes. PIFs are believed to be a consequence...
Mcwilliams, K. A., Yeoman, T. K., Sigwarth, J. B., Frank, L. A., Brittnacher, M.
We examine the large-scale ultraviolet aurora and convection responses to a series of flux transfer events that immediately followed a sharp and isolated southward turning of the IMF. During the...
Mcwilliams, K. A., Yeoman, T. K., Cowley, S. W. H.
Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the...
Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility (2008)
Wright, D. M., Davies, J. A., Robinson, T. R., Chapman, P. J., Yeoman, T. K., Thomas, E. C., ...
SPEAR is a new polar cap HF radar facility which is to be deployed on Svalbard. The principal capabilities of SPEAR will include the generation of artificial plasma irregularities, operation as an...
Yeoman, T. K., Davies, J. A., Wade, N. M., Provan, G., Milan, S. E.
On August 21st 1998, a sharp southward turning of the IMF, following on from a 20 h period of northward directed magnetic field, resulted in an isolated substorm over northern Scandinavia and...
The UV aurora and ionospheric flows during flux transfer events (2008)
Neudegg, D. A., Cowley, S. W. H., Mcwilliams, K. A., Lester, M., Yeoman, T. K., Sigwarth, J. B., ...
Far Ultra Violet (FUV) signatures in the polar ionosphere during a period of magnetopause reconnection are compared with ionospheric flows measured in the cusp ?throat' and dusk cell by the CUTLASS...
HF radar backscatter which has been artificially-induced by a high power RF facility such as the EISCAT heater at Tromsø has been demonstrated to provide ionospheric electric field data of...
Yeoman, T. K., Lewis, R. V., Khan, H., Cowley, S. W. H., Ruohoniemi, J. M.
HF radar data during equinoctial, small IMF By conditions have enabled the ionospheric convection during the substorm growth phase and substorm pseudobreakup to be studied in both hemispheres. This...
The CUTLASS (Co-operative UK Twin Located Auroral Sounding System) Finland HF radar, whilst operating in a high spatial and temporal resolution mode, has measured the ionospheric signature of a...
High-time resolution CUTLASS observations and ground-based magnetometers have been employed to study the occurrence of vortical flow structures propagating through the high-latitude ionosphere during...
Davies, J. A., Yeoman, T. K., Lester, M., Milan, S. E.
During August 1998, the UK EISCAT special programme SP-UK-CSUB, which combines operation of both the mainland VHF and Svalbard UHF incoherent scatter radars, was run for several hours around magnetic...
Davies, J. A., Lester, M., Milan, S. E., Yeoman, T. K.
The CUTLASS Finland radar, which comprises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a...
Milan, S. E., Yeoman, T. K., Lester, M., Moen, J., Sandholt, P. E.
Poleward-moving auroral forms, as observed by meridian-scanning photometers, in the vicinity of the cusp region are generally assumed to be the optical signature of flux transfer events. Another...
Mcwilliams, K. A., Yeoman, T. K., Provan, G.
Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and...
High-latitude HF Doppler observations of ULF waves: 2. Waves with small spatial scale sizes (2008)
The DOPE (Doppler Pulsation Experiment) HF Doppler sounder located near Tromsø, Norway (geographic: 69.6°N 19.2°E; L = 6.3) is deployed to observe signatures, in the high-latitude ionosphere, of...
A study has been performed on the occurrence of pulsed ionospheric flows as detected by the CUTLASS Finland HF radar. These flows have been suggested as being created at the ionospheric footprint of...
A survey of magnetopause FTEs and associated flow bursts in the polar ionosphere (2008)
Neudegg, D. A., Cowley, S. W. H., Milan, S. E., Yeoman, T. K., Lester, M., Provan, G., ...
Using the Equator-S spacecraft and SuperDARN HF radars an extensive survey of bursty reconnection at the magnetopause and associated flows in the polar ionosphere has been conducted. Flux transfer...