The historic arrival of the Cassini spacecraft at Saturn on July 1 2004 marked an intensive observational campaign of the onboard science instruments. The dual technique magnetometer (MAG) detected a rich variety of signatures in the magnetic field of the planet's dynamic plasma environment, which indicated: magnetospheric compression and expansion; encounters with the bow shock and magnetopause boundaries; and subcorotation of the magnetospheric plasma (relative to the planet) at distances > 5 Saturn radii. An overview of these phenomena is given in the context of the global physical conditions in the magnetosphere.

Cassini entered orbit about Saturn on 1st July 2004 providing the first opportunity since Voyager to sample the Saturnian magnetospheric plasma regions. In this presentation we concentrate on the series of magnetopause encounters made by the spacecraft during its inbound trajectory, in particular we present data from the Cassini CAPS Electron Spectrometer (ELS) instrument which measures electrons from 0.58eV-26keV. The ELS instrument collected comprehensive electron data with an unprecedented temporal and energy response throughout the duration of these magnetopause crossings with the timing of the crossings being identified from the change of characteristics of the low energy electron populations. All crossings were made at local times of 07:58 to 08:02 MLT at magnetic latitudes of ~ -15°. The electron density and temperature within the magnetosheath regions were ~ 1.3x10⁵m^-3 and ~ 40eV respectively. Within the magnetosphere the plasma was more rarefied (1.2x10⁴m^-3) with an increased electron temperature of up to several 100eV. The crossings appeared to exhibit varied features associated with different magnetopause configurations. Some are associated with very sharp discontinuities in the electron data, possibly indicating a closed boundary, while others appear to be associated with an interior boundary layer. Some brief magnetosphere entries reveal unusual plasma regions separate from the magnetopause and immersed in the ambient plasma possibly indicating FTE's or boundary layers. We present results from an initial analysis of some of these crossings using the low energy electrons with magnetic field data being used to put the particle results in context.

The Cassini orbit insertion around Saturn provided an excellent opportunity to characterise in depth the magnetic environment of the ringed planet, from the unperturbed solar wind to the inner magnetosphere. During the inbound and outbound pass of the insertion orbit, the Cassini Magnetometer detected multiple bow shock and magnetopause crossings. We comment on the structure and variability of these plasma boundaries implied by the data. We also study the properties of low frequency waves in Saturn's upstream and magnetosheath regions. In particular, observations of non-linear, low-frequency waves called "shocklets", and mirror-mode waves are presented.

The upper atmospheres of the gas giant planets are much hotter than can be explained if solar EUV is the only energy source. Energy inputs associated with magnetosphere-ionosphere coupling currents are thought to play a major role in resolving this energy crisis. These energy inputs take two forms: direct heating of the neutral gas - 'Joule heating' - and acceleration of the neutral gas - 'ion drag'. We discuss the relative magnitude of these two energy sources and their effect upon the upper atmospheric temperature distribution.

In modelling the observed magnetospheric field at Saturn, much work has been done in the so-called "internal field plus disc" approach, where models of the planetary internal field and azimuthal current disc are superposed. However, because magnetopause currents are not considered, these models are restricted to the low latitude inner and middle magnetosphere thus limiting their applicability. In preparation for the arrival of the Cassini spacecraft at Saturn, we have constructed a model that includes a representation of the magnetopause currents.

We find fields due to the magnetopause currents, based on scalar potential functions, which confine the internal and current disc magnetic fields inside a model magnetopause boundary. This approach is similar to that used in the Tsyganenko models of the terrestrial magnetosphere and more recently applied to the jovian and hermean magnetospheres. Our model correctly specifies the seasonally varying tilt between the magnetic dipole axis and the solar wind flow and extends the domain of internal field plus disc models to the whole of the dayside magnetosphere, and also to around -15 RS on the nightside. We describe our methods and note how this improves upon existing global models. The resulting field topology is examined and we compare magnetic fields, obtained from the model, with those obtained by Pioneer 11, Voyager 1/2 and also data from Cassini orbit insertion.

We present an analysis of irregular signatures recorded by the Electron Spectrometer (ELS) on board Mars Express. We then compare with models of the crustal magnetic field on Mars to find significant correlations. The modelled magnetic field direction and the anisotropy of the observed electrons are determined to provide information on the signature's source, and the influence on surrounding plasma regions.

Recent particle-in-cell (PIC) simulations have revealed time-dependent shock solutions for parameters relevant to astrophysical and heliospheric shocks. These solutions are characterised by a shock which cyclically reforms on the spatio-temporal scales of the incoming protons. Whether a shock solution is stationary or reforming depends not only upon the model adopted for electron dynamics, but also on the plasma parameters, notably the upstream beta. For the heliospheric termination shock, these parameters are not well determined: some estimates suggest that the termination shock may be in a parameter regime such that it is time-dependent. It has been pointed out that this may terminate some acceleration processes, for example shock surfing, which have been proposed for time-stationary shock solutions. The introduction of time-dependent electromagnetic fields intrinsic to the shock does however introduce the possibility of new mechanisms for the acceleration of protons. We will discuss the prospects for local ion acceleration at reforming quasiperpendicular shocks, in the presence of pickup ions as seen in selfconsistent PIC simulations with parameters relevant to both SNRs and the heliospheric termination shock.

The evolution of magnetospheric indices on temporal scales shorter than that of substorms is characterized by bursty, intermittent events. These may arise from turbulence intrinsic to the magnetosphere or may reflect properties of the solar wind. This leads to a generic problem of distinguishing between the features of the system and those of the driver. We quantify scaling properties of short term (up to few hours) fluctuations in the geomagnetic indices AL and AU during solar minimum and maximum along with the parameter $\epsilon$ that is a measure of the solar wind driver. Self-similar statistics provide a good approximation for the observed scaling properties of fluctuations in the geomagnetic indices, regardless of the solar activity level, and in the $\epsilon$ parameter at solar maximum. This self-similarity persists for fluctuations on time scales at least up to about 1-2 hours. The scaling exponent of AU index fluctuations show dependence on the solar cycle and the trend follows that found in the scaling of fluctuations in $\epsilon$. The values of their corresponding scaling exponents, however, are always distinct. Fluctuations in the AL index are insensitive to the solar cycle as well as being distinct from those in the $\epsilon$ parameter. We then apply a Fokker-Planck model to obtain the functional form of the probability density function of fluctuations in self-similar quantities.

The determination of propagation times of solar wind conditions at the sunward libration point to the Earth is investigated using mutual information. This provides a quantitative measure of nonlinear correlations between a pair of time series, in this case between solar wind observations, from WIND, and the geomagnetic indices. The success of five commonly used schemes for estimating solar wind propagation times is examined. Propagation assuming a fixed plane normal at 45° to the GSE x-axis (i.e. the Parker Spiral estimate) is found to give optimal mutual information. The mutual information depends on the point in space chosen as the target for the propagation estimate, and we find that it is maximised by choosing a point in the nightside rather than dayside magnetosphere. In addition, we employ recurrence plot analysis to visualise contributions to the mutual information, this suggests that it appears on timescales of hours rather than minutes.

Since 1990, the Ulysses mission has studied the previously unexplored third dimension of the heliosphere from an elliptical orbit tilted at approximately 80° to the solar equatorial plane. Here we present an ongoing attempt to understand the topology of the heliospheric magnetic field through solar maximum by studying spacecraft observations of the heliospheric current sheet (HCS). The dataset studied (April 2000 - June 2002) is centred on aphelion, includes the solar maximum south and north polar passes, and extends either side back down to latitudes of 50° and 40° in the south and north, respectively. Encounters with the HCS by Ulysses are observed at all latitudes in the southern hemisphere and up to 67° in the north. For each encounter the local orientation of the HCS has been obtained using the minimum variance technique. The results show an increase in the spread of the north-south elevation angle of the orientations with increasing latitude, most pronounced at high (>50°) southern latitudes. The orientations are consistent with the single highly tilted HCS previously inferred from the latitudinal distribution of Ulysses encounters during the second orbit at solar maximum.

ESR data from the first two SPEAR campaigns in April/May and September/October 2004 are presented. These indicate that the SPEAR high power beam has been able to artificially enhance both the ion and plasma line spectra. The enhanced lines are generally well correlated with one another and persist throughout the period when SPEAR is on in ordinary mode. Unlike typical results seen previously in heating experiments at Tromsø, there appears to be no consistent overshoot effect in the ESR/SPEAR results. However, there is clear evidence for the excitation of the parametric decay instability as well as the so called purely growing mode.

We examine the effects of sub-auroral polarisation streams (SAPS) on the mid-latitude ionosphere. SAPS and other penetrating electric fields (PEFs) may increase F-region density by an order of magnitude, and these density changes have significant impact on TEC measurements, GPS ray paths, and over-the-horizon (OTH) radar. We model the effects of SAPS with the coupled thermosphere ionosphere plasmasphere model (CTIP), comparing the results with those of the Utah State University model.

The production of small-scale plasma irregularities in experiments undertaken at the EISCAT heating facility in Tromsø have been observed using the CUTLASS Finland radar. Presented here are some results examining the width and symmetry of the patches of artificial irregularities. Effects of the beam shape, magnetic field and upper hybrid geometry are examined and finally a comparison made with new results from the SPEAR radar on Svalbard.

We present the ionospheric flow response to magnetic reconnection which occurred under various interplanetary magnetic field conditions, using SuperDARN HF radars to collect the ground based data, ACE spacecraft to characterize the upstream IMF conditions, and DMSP satellites to identify the location of the open-closed field line boundary. Estimating the location of the open-closed field line boundary suggests that when the IMF is northward boundaries are located at higher latitudes than when the IMF has a strong positive B_y component. Our studies show that when there is a transition in IMF orientation, it affects the northern hemisphere much quicker than the southern hemisphere we speculate is due to the tilt in the Earth axis at spring equinox.

The EUV imager onboard the IMAGE satellite can provide line-of-sight helium ion densities of the plasmasphere. What is not known is the density distribution along that line-of-sight. Using CTIP model data we test various methods of extracting this information and then apply our methods to storm time data from the IMAGE satellite.

This presentation will describe progress on the development of AstroGrid (http://www.astrogrid.org), the UK's Virtual Observatory. The project is building a grid of interoperating data archives and software tools, with the aim of facilitating comparison of data from diverse sources, and enabling large scale complex analyses, including data mining. An example of usage of AstroGrid to manipulate solar data will be presented, showing how movies tracing the evolution of a user defined solar feature from multiple datasets can be generated. Developments in the Solar Terrestrial Physics area will be discussed, including the science case aimed at the study of Magnetic Storm Onsets.

The new SPEAR high power RF facility on Svalbard ran its first campaigns in 2004. In September/October 2004 the first observations were made of artificially induced coherent backscatter from the CUTLASS radars. These demonstrate that the SPEAR high power beam has been able to artificially enhance the thermal plasma instabilities required for artificial backscatter generation. The HF propagation modes of CUTLASS, and the backscattered power, spectral width and velocity measurements from these first observations will be presented, and the implications for the future SPEAR science programme discussed.

DE 2 Wind And Temperature Spectrometer (WATS) instrument data has been analysed to investigate supersonic excursions of the measured neutral wind. 488 supersonic events have been identified, with the zonal component of the neutral wind Mach number M in the range 1 < M < 2. These events are located in the polar cap, predominantly between 75° and 85° MLT in the dawn sector. The events are located broadly spread over the height range 300 - 600 km. The mean horizontal linear extent of the regions of supersonic flow is estimated to be around 140 km. We find an anticorrelation between Mach number (for 1 < M < 2) and neutral temperature, which may be due to adiabatic cooling of the thermosphere from thermospheric heat sources below the satellite altitude.

Observational evidence suggests that standing Alfvén waves excited on freely oscillating geomagnetic field lines could be a viable mechanism for pulsations in the ULF range. By approximating the oscillations on terrestrial field lines as Alfvén waves standing on individual field lines, the period of oscillation can be estimated using a time-of-flight approximation. We shall therefore present the results of time-of-flight estimates employing the 1996 Tsyganenko magnetospheric magnetic field model and contrast these to the findings of previous studies.

The Cluster PEACE instruments are periodically turned on in the outer radiation belt as part of the Cluster chorus studies. However, the PEACE data in this hostile environment are contaminated by high count rates due to penetrating radiation belt electrons. We estimate that there are 5-6 mm of aluminium equivalent shielding so that the threshold for penetration is approximately 2 MeV. The flux of these relativistic electrons in the outer radiation belt is highly variable and can vary by a factor of ~1000 over a period of hours to days during storms. Penetrating radiation is thus likely to be a problem, of varying severity, during the Cluster perigee passes. Each Cluster spacecraft is equipped with two different PEACE sensors. HEEA is optimised to cover the higher energy range, while LEEA is optimised to cover the lower energy range. The geometric response of HEEA is larger than that of LEEA by a factor of ~3.75, as appropriate for the lower fluxes found at higher energies. The different geometric responses can be used to separate the true plasma counts from the counts due to penetrating radiation. In this presentation we discuss our technique and present some initial results that suggest that it will be possible to correct the data and obtain the true plasma counts.

We present Cluster observations of the high-altitude northern hemisphere cusp region on 16 March 2002, during a steady, extended period of positive IMF B_y and B_z. Cluster moved into the high-altitude cusp through its poleward boundary and towards its equatorward boundary while remaining near local noon. SuperDARN and IMAGE data imply the existence of two reconnection sites somewhere on the magnetopause. One of these appears to be in the high-latitude dawn sector (component merging site) while the other is in the dusk sector. The latter site is a likely place for anti-parallel reconnection. Dawnward convection inside the cusp suggests that Cluster observed particle injections from the dusk reconnection site. Inside the cusp, Cluster crossed 3 regions with different plasma properties. For the first hour, strong injections of magnetosheath-like plasma were observed, indicating that Cluster crossed newly-reconnected field lines near the poleward boundary of the cusp. During the second hour, Cluster was in the Stagnant Exterior Cusp (SEC) region, characterized by nearly isotropic stagnant plasma as well as a magnetic field depression. For 10 minutes prior to entering the magnetosheath, Cluster crossed a region with significant anti-field-aligned flows. The observations inside the SEC can not be explained by simple reconnection models or by wave/particle interactions. We suggest that the SEC region exists on newly re-closed field lines, reconnected first in the northern hemisphere and later reconnected in the southern hemisphere. We show that Cluster observations inside the different regions correspond to the theoretical expectations from this 'double reconnection' model.

We present Cluster, Double Star and SuperDARN observations during a close magnetic conjunction on May 8, 2004. The 2 spacecraft were in the dawnside flank of the magnetosphere, with Double Star located near the equatorial plane and Cluster at higher geographic Southern latitudes. Double Star observed FTE signatures on the magnetopause for almost 8 hours (between 08:00-16:00 UT). Around 08:30UT, Cluster crossed the magnetopause in the same MLT sector as Double Star, and observed field-aligned injections of magnetosheath electrons just inside the magnetopause for a period of 2 hours. Finally, strong convection enhancements in the return flow of the dawnside conjugate ionosphere were simultaneously observed by the SuperDARN radars in the Northern Hemisphere. We discuss the connection between the observations made by Cluster, Double Star and SuperDARN, with particular reference to the reconnection geometry on the dawnside magnetopause, solar wind conditions and the location of the injections site(s) observed by Cluster and Double Star.

At ~1020 UT on October 20, 2001, a substorm onset occurred and was identified by the FUV instrument on the IMAGE spacecraft. At this time the four Cluster spacecraft were located at (-13,11,5) Re GSE, in the near-vicinity of the plasmasheet. Prior to the substorm onset, large scale magnetotail motion resulted in the 4 spacecraft making several complete crossings of the entire plasmasheet. Using multispacecraft techniques, we have established that during these pre-onset crossings the plasmasheet was relatively thin (<1 Re) and strongly tilted, with the normal to it surface almost along the Y GSE direction. Moreover, significant electron currents and anisotropic phase space distributions were detected by the Cluster PEACE instruments in the PSBL before the onset. After the onset, plasmasheet expansion took place and highly-anisotropic electron distributions were observed in the central plasmasheet. In this paper we present an analysis of these distributions and discuss the different possible origins of the observed electron anisotropies.

The Cluster spacecrafts crossed through the southern magnetospheric cusp several times during the geomagnetic storm period 24 October - 03 November 2003. Analysis of the Cluster data from the FGM, CIS and STAFF instruments, solar wind and IMF data from ACE and Geotail, and ground-based data from EISCAT and magnetometers provide evidence for the magnetosheath-cusp population by solar wind compression during the early main phases of the storms on 24 and 29 October, with strong magnetic field fluctuations and magnetic wave intensity. The Cluster crossing on 24 October occurred during the early main phase of a moderate geomagnetic activity. A strong solar wind (speed 600 km s^-1, density up to 80 cm^-3 and pressure over 10 nPa) arrived ACE at 14:47:15 UT and IMF B_z turned strongly northward. At the speed of 600 km s^-1, the solar wind took about 38 min to reach Cluster. At the arrival of the strong wind at Cluster (15:25:15 UT), which was entering the cusp from the magnetosheath, the ion density (H⁺, He⁺⁺ and O⁺) suddenly increased over 400 times, ion temperature increased over 10 times and ion velocity turned strongly southward (-300 km s^-1). The EISCAT UHF and VHF radars at Tromsø showed associated changes in electron density, electron and ion temperatures, and ion velocity. Similar events happened during the early main phase of the severe geomagnetic storm on 29 October when an abnormally strong solar wind (speed around 1500 km/s; pressure and density not available) arrived ACE at 05:58:28 UT and IMF B_z fluctuated around zero. The events at Cluster started about 13.5 min later when the wind reached the spacecrafts, which were again entering the cusp from the magnetosheath.

In Cooling et al. (2001) we presented a model for predicting the motion of open flux tubes along the magnetopause following magnetic reconnection on the dayside. The model assumed a paraboloid magnetopause. The magnetosheath field at the magnetopause was derived from the work of Kobel and Fluckiger (1994), and a simple geomagnetic representation of the geomagnetic field was used. Velocity and density parameters were derived from Spreiter et al. (1966). Our model allows the user to choose either an anti-parallel or component approach to reconnection by selecting locations from where to initiate the reconnection process accordingly. We also allow the user to set a minimum current density threshold below which reconnection may not occur. As an adjunct to our model, we present a catalogue of modelled parameter maps for a full range of 27 IMF orientations, including positive, zero and negative B_x components of the IMF. To date the catalogue includes, for an IMF of field strength 10nT : the magnetosheath field at the magnetopause derived from KF94, the magnetopause current densities derived from the coupling of the KF94 model and our simple geometrical geomagnetic model, and lastly the magnetic shears derived from the same models. The last also includes overplots of the 35nT and 50nT threshold contours. We also include in the catalogue the IDL code used to generate the flux tube motion plots demonstrated in Cooling et al (2001). The catalogue is available on-line at www.coolbeesplace.com/catalogue.html. This paper gives an overview of the material currently available.

A fully kinetic theory of mirror type modes accounting for the finite ion Larmor radius effect (FLR) in non-Maxwellian space plasmas is developed. A general mirror mode dispersion relation for the arbitrary velocity distribution in a fully kinetic limit is obtained. A close inspection of this dispersion relation shows that it describes two different instabilities. The first one corresponds to the classical mirror instability which growth rate attains the maximum value at the wavelengths of the order of the ion gyroradius. In addition, we found that if plasma is mirror stable, i.e. when the condition for the mirror instability is not satisfied, the plasma can still be unstable. The instability in this case arises in the presence of the halo on the tail of the ion distribution function. This new instability that we term as halo instability arises when the ratio of halo and thermal velocities exceeds a certain critical value. A compact expression for the instability growth rate is obtained. The results of the theory are applied to existing satellite observations.