http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10692 Research Doctorate - Doctor of Philosophy (PhD) 2013-03-21T06:01:14.677Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:12033 The occurrence of Pcl-2 ULF waves in Scott Base and Casey Antarctic magnetometer data has been examined with the objective of determining whether the source region for these waves is located in the Earth's cusp/boundary layer region or the magnetosheath. In particular we explore the hypothesis that some Pcl-2 events are propagated along open field lines which convect over the southern polar cap. For a selected event the location of Scott Base with respect to the open/closed field line boundary was independently determined using DMSP spacecraft particle data and well established particle energy and flux criteria. This event provides evidence that Pcl-2 waves can be seen on the ground well inside the polar cap. The possibility of propagation in the ionospheric waveguide, away from the footpoint of the source, is investigated using numerical modelling and realistic ionospheric parameters. Under the modelled conditions we find a modification of wave ellipticity which excludes this explanation for the polar cap Pcl-2 seen in the event study. 2012-11-19T03:26:42.711Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3305 The cold, core plasma mass density in the Earth's magnetosphere may be deduced from the resonant behaviour of ultra-low frequency (ULF; 1–100 mHz), magnetohydrodynamic (MHD) waves. Ground-based magnetometers are the most widely used instruments for recording the signature of ULF wave activity in the magnetosphere. For a suitable model of the background magnetic field and a functional form for the variation of the proton number density with radial distance, the resonant frequencies of ULF waves provide estimates of the equatorial plasma mass density. At high latitudes, the magnetic field model becomes critical when estimating the plasma mass density from FLR data. We show that a dipole field model is generally inadequate for latitudes greater than ~65° geomagnetic compared with models that are keyed to magnetic activity, interplanetary magnetic field and solar wind properties. Furthermore, the method often relies on the detection of the fundamental ULF resonance, which changes frequency depending on the polarisation of the oscillation. Using idealised toroidal and poloidal oscillation modes, the range of the derived densities as the ULF wave polarisation changes is of the same order as changing the density function from a constant value throughout the magnetosphere to assuming constant Alfven speed in a dipole geometry. 2012-05-29T00:38:47.392Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:2808 Induction magnetometer data recorded at three closely spaced sites (~120 Km) in Antarctica (mlat ~−75°) have been examined for ionospheric signatures of the cusp/cleft region of the magnetosphere. Crossphase analysis of the 1-10 mHz band, using pure-state filtering techniques reveal diurnally varying field line resonances embedded in the spectra, while interstation phase lag measurements indicate azimuthal propagation of waves away from local magnetic noon. Using the T89 external field model crossphase measurements are put in the context of diurnally changing field line topology due to compression at the subsolar region and stretching along the dawn and dusk flanks. On six of the eight days of this study we have identify a consistent two dimensional phase pattern projected in the dayside ionosphere, indicating closed field lines thread these sites during periods of low to moderate geomagnetic activity (Kp<3). 2012-03-12T07:22:24.080Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1122 The spatial structure of ultralow frequency (ULF) waves is usually, though not exclusively, estimated from ground-based magnetometer measurements. This paper compares ULF wave spatial structure obtained from coincident ground magnetometer and HF radar measurements and addresses the interpretation of Pc5 azimuthal wave numbers. ULF spatial structures estimated from magnetometer and radar data were quite different for the October 23, 1994, event presented by Ziesolleck et al. [1998]. Azimuthal wave numbers (m) were 3–5 and 12 for the ground and ionosphere, respectively. We reexamine this event and attempt to explain why the spatial structure of the ULF wave in the ionosphere, seen by the Saskatoon Super Dual Auroral Radar Network (SuperDARN) radar, may differ from that deduced from the magnetometer data. The radar data are used to develop a two-dimensional (2-D) model of the spatial distribution of ULF amplitude and phase in the ionosphere. Our modeling shows that the differences between ground and ionosphere measurements may be explained by spatial integration. In general, m numbers deduced from ground measurements should be smaller than the ionospheric values, and they are strongly dependent on the ionospheric ULF amplitude and phase distribution in both latitude and longitude. 2012-03-12T07:14:38.825Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1137 Plasmaspheric ducts may execute Doppler oscillations driven by propagating ultra-low frequency (ULF) waves. We examined about 100 such events recorded over 1 year under magnetically quiet conditions at L = 2.5 using artificially generated whistler-mode VLF signals and ground magnetometers. Joint peaks in the VLF Doppler and magnetometer spectra occurred at the frequency expected for ULF waves generated by the ion-cyclotron instability in the upstream solar wind. The VLF Doppler shifts are most likely due to radial motion of flux tubes of a few kilometers, driven by the east-west electric field of propagating ULF waves. When the frequencies match, the incoming wave energy also couples to standing poloidal and azimuthal field line oscillations, producing field line resonance signatures in both the D and H components on ground-based magnetometers. The phases of the VLF and ULF oscillations are consistent with ionospheric rotation of the downgoing ULF wave field. Since the scale size of VLF flux tubes is significantly smaller than for ULF flux tubes, VLF Doppler observations can provide more precise spatial information on ULF wave fields in the plasmasphere. Furthermore, it should be possible to use ULF oscillations to monitor the formation of quarter wavelength mode standing field line oscillations when the conjugate ionospheres have different conductivities. 2012-03-12T07:14:30.762Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:2003 This paper discusses the use of ground magnetometer data to derive plasma mass density profiles of the dayside plasmapause region with spatial and temporal resolution in the range 0.15–0.4 RE and 20–60 min. This is achieved using cross-phase techniques to identify field line resonance signatures that are not apparent in power spectra. Under quiet conditions, mass density profiles do not show a distinct plasmapause and closely resemble electron density profiles for similar conditions. Under more active conditions the plasmapause can be clearly identified, and its width can be resolved in about 20% of the cases. Spatial integration effects smooth the mass density profiles near the plasmapause boundaries, while comparison of the mass and electron densities allows estimates of the heavy ion mass loading. Temporal variations in the plasmapause position and plasmaspheric density depletions are readily resolved. Sudden changes in solar wind conditions cause a redistribution of plasma within ~20 min, probably in response to penetration of the magnetospheric electric field into the plasmasphere. Field line resonances occur daily and provide a useful tool for investigating the plasmapause region, especially in conjunction with VLF whistler and in situ particle and imaging experiments. Furthermore, the extensive existing suites of magnetometer data permit retrospective studies of focus intervals. 2012-03-12T07:14:06.421Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3260 An array of magnetometers and Doppler sounders spanning L = 1.56–2.77 was used to examine perturbations in the daytime ionosphere driven by downgoing ULF waves. For frequencies away from the local field line resonance (FLR), the waves caused mostly vertical motions of the F-region plasma with amplitude ∼0.03–0.06 Hz/nT, with a phase delay of 30° to 40° at the ground. At the local resonant frequency and harmonics the amplitude and phase delay increased markedly. We modeled this by considering an admixture of ULF wave modes and oblique magnetic field geometry, and using actual ionospheric parameters. The model results agree well with observations when the downgoing wave mode varies smoothly from pure fast mode away from the resonance to mostly transverse mode at resonance. These results provide new information on the interaction between downgoing ULF waves and the ionospheric plasma. 2012-03-12T07:05:11.059Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3311 We present a simple time-of-flight analysis of Alfvén pulsations standing on closed terrestrial magnetic field lines. The technique employed in this study in order to calculate the characteristic period of such oscillations builds upon earlier time-of-flight estimates via the implementation of a more recent magnetospheric magnetic field model. In this case the model employed is the Tsyganenko (1996) field model, which includes realistic magnetospheric currents and the consequences of the partial penetration of the interplanetary magnetic field into the dayside magnetopause. By employing a simple description of magnetospheric plasma density, we are therefore able to estimate the period of standing Alfvén waves on geomagnetic field lines over a significantly wider range of latitudes and magnetic local times than in previous studies. Furthermore, we investigate the influence of changing season and upstream interplanetary conditions upon the period of such pulsations. Finally, the eigenfrequencies of magnetic field lines computed by the time-of-flight technique are compared with corresponding numerical solutions to the wave equation and experimentally observed pulsations on geomagnetic field lines. 2012-03-12T06:56:31.779Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3307 The cold, magnetized plasma in the Earth's magnetosphere supports two ultralow- frequency plasma wave modes. Both these modes may exhibit resonant oscillations in the magnetosphere cavity. Theoretical and numerical studies have predicted the existence of cavity/waveguide resonance modes, yet experimental evidence is sparse. In this paper we detail the expected structure of these modes using both one dimensional (1-D) and three-dimensional (3-D) magnetohydrodynamic (MHD) numerical models. The cavity/waveguide mode structures are examined in order to develop experimental detection methods suitable for spacecraft electric and magnetic field perturbation data. Cavity mode resonances in the 1-D model suggest a detection method based on wave polarization using the radial (bx) and field-aligned (bz) magnetic perturbations. However, when implemented, this method failed to identify cavity/waveguide modes in the magnetic field data recorded by Active Magnetospheric Particle Tracer Explorers/CCE for events that showed pronounced field line resonances in the azimuthal (by) channel. An examination of data from a 3-D MHD numerical simulation showed that the cavity/waveguide resonant signature was identified best in bz component data. Consequently, a wave mode detection method using the bz data from two spatially separated satellites is discussed. Magnetometer data examples from the ISEE 1 and 2 spacecraft show that field line resonances appear in the by data even when the coherence length of the bz data is less than 0.4 RE. 2012-03-12T06:56:29.137Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3308 The propagation of ultra low frequency (ULF; 1-100 mHz) waves from the magnetosphere to the ground is examined in the presence of oblique background magnetic fields. The problem is developed analytically for a thin sheet ionosphere, neutral atmosphere, and perfectly conducting ground. The cold plasma, ideal magnetohydrodynamic (MHD) Alfvén wave modes are assumed to propagate in the MHD medium above the ionosphere. A reflection and wave mode conversion coefficient matrix (RCM) is derived which describes mixing and conversion between shear Alfvén and fast mode energy when interacting with the ionosphere/atmosphere/ground system. The RCM is found to depend in a complicated way on the background magnetic field dip angle, the horizontal wave vector, and the conductivity of the ionosphere. For an oblique background magnetic field, →B₀ in the XZ plane, the perpendicular wave number, ky, is shown to be a critical parameter that determines reflection and mode conversion characteristics. This study also highlights the need for spatial information of ULF wave energy in order to interpret experimental ULF wave data recorded at ground level in terms of magnetospheric processes. 2012-03-12T06:56:26.355Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:4836 We have examined the diurnal variation of the local field line eigenfrequency at L ~ 2.6 using cross-phase analysis of Sub-Auroral Magnetometer Network and Magnetometers Along the Eastern Atlantic Seaboard for Undergraduate Research and Education ground magnetometer array data. On several days the eigenfrequency was remarkably low near the dawn terminator, when one end of the field line was sunlit and the other end was in darkness. Later in the morning the eigenfrequency gradually increased to the normal daytime value. This type of diurnal eigenfrequency variation was found in both European and American meridians and in several seasons (March, June, and December). By modeling this situation we show that the extraordinarily low eigenfrequency events appeared when the ionospheric Pedersen conductance was strongly asymmetric between both ends of the field line, leading to the formation of quarter-wavelength-mode standing waves that revert to half-wavelength modes as the dawn terminator passes both conjugate points. Ground-based magnetometer measurements of local toroidal field line eigenfrequencies are often inverted to infer plasma mass density in the magnetosphere by assuming half-wavelength-mode standing field line oscillations. However, the mode structure and hence field line eigenfrequency also depend on the ionospheric conductance. In particular, we find that there is a threshold of interhemispheric conductance ratio for the quarter-wavelength mode to be established. Our results therefore show that cross-phase techniques can detect quarter-wavelength-mode waves, where the inferred mass density would be overestimated. 2012-03-12T06:53:12.897Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:4837 The magnetised plasma of the near-Earth space environment supports ultra-low frequency (ULF; 1 - 100 mHz), magnetohydrodynamic (MHD) oscillations. For sufficiently large ionospheric conductances, field line resonances (FLRs) form between the northern and southern ionospheres. These conditions are usually met for daytime ionosphere conductance values. The FLRs are normal modes of the system and may be used to remote sense plasma mass densities in the magnetosphere. The oscillations lose energy in the ionosphere whose properties determine the boundary conditions, particularly resonance damping effects. Using a two dimensional (2D) MHD model of the magnetosphere and realistic ionosphere boundary conditions, the variation in resonant frequency with ionosphere conductivity is reported. For typical mid to low latitude summer and winter ionosphere parameters, the FLRs change by less than 5%. This translates to an uncertainty of 7% in plasma mass density. 2012-03-12T06:53:12.728Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:7818 The concept of a geomagnetic field line has been widely used in the study of magnetospheric physical phenomena. For example, the mode in which ULF waves propagate relates to the direction of the field, with the Alfven wave mode propagating along the field direction. Very little is known about the perpendicular extent of the propagating wave. In this paper, wave coherency methods are utilized to analyze ULF waves in the Pc3 band that were simultaneously observed by the Cluster satellites near the exterior cusp and by ground stations at local magnetic noon near the footprint of the cusp. The results show that the coherency of waves observed at the ground on the H component is much larger than that on the D component, which is opposite to that seen by Cluster in space. The coherency between the H component on the ground and the y component in space was higher than the other combination of pairs, with the coherency between the satellite and the Daneborg (DNB) station having the maximum value. These results suggest that the polarization of the waves are rotated by 90° after propagating through the ionosphere, and the magnetic footprint of Cluster is closest to the DNB station at this time. The coherency of the Pc3 waves between the satellites is highly related to the alignment of satellite pairs with respect to the geomagnetic field direction. This alignment may provide a transverse-scale size of the geomagnetic Pc3 ULF waves near the exterior cusp at ~900 km with a coherency of 0.65. 2011-06-02T06:00:30.473Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3478 The outer radiation belt injection, transport, acceleration and loss satellite (ORBITALS) is a small satellite mission proposed as a Canadian contribution to the satellite infrastructure for the International Living With a Star (ILWS) program. The ORBITALS will monitor the energetic electron and ion populations in the inner magnetosphere across a wide range of energies (keV to tens of MeV) as well as the dynamic electric and magnetic fields, waves and cold plasma environment which govern the injection, transport, acceleration and loss of these energetic and space weather critical particle populations. ORBITALS will be launched around 2010–2012 into a low-inclination GTO-like orbit which maximizes the long-lasting apogee-pass conjunctions with both the ground-based instruments of the Canadian Geospace Monitoring (CGSM) array as well as with the GOES East and West and geosynchronous communications satellites in the North American sector. Specifically, the ORBITALS will make the measurements necessary to gain fundamental new understanding of the relative importance of different physical acceleration and loss processes which are hypothesised to shape the energetic particle populations in the inner magnetosphere. The ORBITALS will also provide the raw radiation measurements at MEO altitudes necessary for the development of the next-generation of radiation belt specification models, and on-board experiments will also monitor the dose, single-event upset, and deep-dielectric charging responses of electronic components on-orbit. In this paper we outline the scientific objectives of the ORBITALS mission, discuss how the ORBITALS will lead to solutions to outstanding questions in inner magnetospheric science, and examine how the ORBITALS will complement other proposed inner magnetosphere missions in the ILWS era. 2010-09-22T01:40:01.666Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:2240 Electromagnetic ion cyclotron (EMIC) waves are generated in the equatorial region of the plasmasphere-magnetosphere by internal wave-particle interaction with ring current ions. In ground observations they are observed as Pc 1-2 (0.1-5 Hz) waves, and one group of waves exhibits a spectral fine structure that has been classically explained by bouncing packet field-aligned propagation. An unstructured class of Pc 1-2 waves, including intervals of pulsations with diminishing period, lacks a fine structure pattern and is the dominant emission observed in the middle and outer magnetosphere by satellites. Poynting flux observations show that wave energy propagates unidirectionally away from the equatorial region, which does not support the bouncing wave packet paradigm. The cold/cool magnetospheric plasma has a profound effect on the generation and spectral properties of EMIC waves. The waves are often observed at geostationary orbit within the outer magnetosphere extension of plasmaspheric plasma plumes seen by the IMAGE spacecraft in the extreme ultraviolet (EUV) imager instrument and associated with subauroral proton arcs seen by the far ultraviolet (FUV) imager. This provides evidence in support of a ring current loss mechanism induced by pitch angle scattering of protons by EMIC waves. Characteristic frequencies introduced into the cold/cool plasma by heavy O[+] and He[+] ions determine the EMIC wave spectra and these may be used in plasma diagnostic studies. Outstanding issues considered include the possible role of the ionospheric Alfvén resonator in EMIC wave generation, and the modulation of EMIC waves by Pc 3-5 long-period ULF waves. 2010-04-27T06:53:58.157Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1997 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 modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B₀, giving an e×B₀ drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF) Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere. 2010-04-27T06:45:51.944Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1993 Measurements of ionospheric E x B drifts obtained with HF radars from the SuperDARN (Super Dual Auroral Radar) Network sometimes show signatures of ULF (few mHz) waves. We present a new data display technique that facilitates the detection of ULF waves in both ground and sea scatter returns. Statistical study of high time resolution data from the SuperDARN TIGER radar in Tasmania, Australia, revealed that ULF wave signatures occur on an everyday basis with ground scatter accounting for about 60% of wave events. About half of these events exhibit high coherence across large spatial distances and are associated with ULF pulsations recorded by a ground magnetometer. These results show that SuperDARN radars may be used to routinely monitor ULF waves in the high-latitude ionosphere. 2010-04-27T06:45:49.310Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:2395 Recent IMAGE satellite EUV helium density observations of plasmaspheric plumes extending beyond the plasma pause into the plasma trough region of the magnetosphere have been associated with sub-auroral proton arcs observed by the IMAGE FUV instrument.Also proton precipitation has been associated with electromagnetic ion cyclotron (EMIC) waves seen on the ground as Pcl-2 ultra-low frequency (ULF) waves. This evidence suggests a relationship between plasma plumes, proton precipitation and EMIC waves, and supports the EMIC wave-particle interaction with ring current ions as a possible ring current loss mechanism. Using high-resolution (0.5 s) fluxgate magnetometer data from the GOES-8 and GOES-10 geosynchronous satellites we show two case studies on 9-10 and 26-27 June 2001, where EMIC waves in the 0.1-0.8Hz frequency range are observed within plasma plumes extending to the geosynchronous orbit. These plumes are also seen in LANL geosynchronous satellite MPA data. The results suggest that EMIC waves may be preferentially generated in enhanced plasma density created by the plasma plume. The EMIC waves are unstructured and have the properties of the well-known intervals of pulsations with diminishing period (IPDP) seen on the ground and in space in the afternoon sector. There are classical EMIC transverse waves showing left-hand circular and elliptical polarization below the helium cyclotron frequency. The observation of a slot in the wave spectrum suggests the presence of He⁺ ions with relative concentrations in the range 6-16%, in a predominantly H⁺ plasma. This is consistent with the IMAGE-EUV He⁺ observations of plasma plumes. 2010-04-27T06:20:01.241Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1768 The structure of the density discontinuity across the plasmapause is often based on electron and H+ density profiles with the contribution of heavy ions (He+, O+ etc) neglected. Electron and ion density measurements in this region may differ significantly due to the presence of heavy ions and it is important for the intercomparison of different datasets to understand these differences. Dynamics Explorer (DE-1) magnetic field and plasma composition data have been used to compare heavy ion responses across the plasmapause and to calculate the mass loaded ion density (ρ) profiles. To illustrate this we investigate mass loading through radial profile variations in the Alfven velocity (VA). Results show that the gradient in ρ and VA across the plasmapause is modified when mass loading due to multiple heavy ion species is included, particularly in the presence of the O+ torus. Application to ultra-low frequency (ULF) field line resonance is used as an example where the contribution from heavy ions smoothes out the expected ULF wave resonant frequency discontinuity at the plasmapause. 2010-04-27T06:10:31.208Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1089 Significant similarities have been identified in the dynamic power spectra of induction magnetometer data recorded at the conjugate cusp stations of Davis, Antarctica (mlat -74.3, mlong 101.5) and Longyearbyen, Svalbard (mlat 75.0, mlong 114.5). A 60 day period in 1993 (January-February) has been studied to characterise two common features, 1) Broadband Pc5 bursts which predominantly occur 2-4 hours before and after local magnetic noon, and which exhibit polarisations suggestive of a Kelvin-Helmholtz-like source mechanism, and 2) A resonance structure which has’ an arch-shaped local time dependence. Interhemisphere phase measurements indicate oddmode toroidal standing-waves after field line resonance and azimuthal propagation effects are taken into account. Phase studies such as this may be used to study conjugacy at high latitudes and identify the location of the open and closed field line boundary, an important diagnostic parameter in space weather studies. 2010-04-27T06:06:33.073Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:480 The north-south asymmetry of the amplitude of ULF pulsations in the Pc 3-5 band is studied using magnetic field data from the magnetically conjugate stations at L similar to 5.4: Kotzebue (KOT) in the northern hemisphere and Macquarie Island (MCQ) in the southern hemisphere. We obtained the following results for the northward (H) component of magnetic pulsations: (1) The north to south power ratio shows a maximum in the northern winter and a minimum in the northern summer. This "seasonal variation'' is stronger at higher frequencies (Pc 3 and Pc 4 frequencies). (2) The north to south power ratio for the Pc 4 and Pc 5 frequency band is basically greater than 1.0 for all seasons. This "positive offset'' is stronger at lower frequencies. The "seasonal variation'' implies that the magnetohydrodynamic (MHD) waves incident from the magnetosphere are more strongly shielded when the ionospheric conductivity is higher. The "positive offset'' may result from the difference of the background magnetic field intensity between KOT and MCQ. 2010-04-27T05:47:43.128Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:5940 The magnetised plasma of the near-Earth space environment supports ultra-low frequency (ULF ;1-100 mHz), magnetohydrodynamic (MHD) oscillations in predominantly two wave modes. The fast Alfvén mode spreads ULF wave energy isotropically throughout the magnetosphere. For sufficiently large ionospheric conductances the shear Alfvén mode forms field line resonances (FLRs) between the northern and southern ionospheres. These conditions are usually met for daytime ionosphere conductance values. The FLRs are used to remotely sense plasma mass densities in the magnetosphere. The oscillations lose energy in the ionosphere, whose properties determine the boundary conditions, particularly by resonance damping effects. Using a MHD model of the magnetosphere with realistic ionosphere boundary conditions, the variation in resonant frequency with ionosphere conductance is reported. The effects of the ionospheric conductance on the ULF wave fields along the resonant field lines are also shown. The finite Pedersen and Hall conductances dissipate wave energy into the ionosphere and the spatial and temporal distributions of this energy show a distinct poleward propagation. 2010-04-27T04:32:03.121Z ]]>