As society moves towards greater dependence on technology, understanding and predicting extreme Space Weather becomes increasingly important. Indeed, the complex, simultaneous interplay between multiple phenomena can unpack further insight into Space Weather effects. Thanks to decades of in-situ and ground observations, long archives of Space Weather measurements are ripe for exploitation by more complex, data intensive techniques. In this study, three decades of in-situ and ground observations of Earth’s Space environment are leveraged to model the joint extremal behaviour of solar wind driving and internal geomagnetic responses, using Bivariate Extreme Value Analysis. While often utilised in other fields with more long-term and/or higher spatial resolution datasets (such as meteorology), this is the first application of this technique in more than one dimension in the field of space plasma physics. An initial result is that upstream and internal variables exhibit weaker extremal dependence on minute timescales than on hourly timescales, in line with characteristic magnetospheric coupling timescales. Specifically, the joint extremal behaviour of a solar wind coupling function with the auroral electrojet index AE is explored and predicted. This modelling enables estimation of a 75-year return period for the 2003 Halloween geomagnetic storm.

Using a substorm onset list from the Imager for Magnetopause to Aurora Global Exploration (IMAGE) and Polar satellite images, we have constructed a new dataset of 63 substorm onsets observed in both hemispheres and their locations. We find that incorporating the history of the interplanetary magnetic field (IMF) improves the predictive power of IMF By in explaining conjugate displacement in Magnetic Local Time (MLT). Our dataset, approximately five times larger than in previous studies, enhances statistical power and focuses on the substorm onset feature. This allows for better correlation of IMF By with MLT conjugate displacement (ΔMLT), since it has been shown that IMF-induced By tends to diminish as substorms progress. In line with previous work, we find a linear relationship between IMF By and ΔMLT, though with a shallower gradient. Additionally, we analyse predictors of conjugate displacement in Magnetic Latitude (ΔMLat), showing that dipole tilt (ψ) is the strongest predictor. However, we find that this relationship is not strictly linear, and that a larger dataset and a better understanding of the physical mechanisms are needed to more accurately capture the exact functional relationship between ψ and ΔMLat.

Understanding global space weather effects is of great importance to the international scientific community, but more localised space weather predictions are important on a national level. In this study, data from a ground magnetometer at Valentia Observatory is used to characterise space weather effects on the island of Ireland. The horizontal component of magnetometer observations and its time derivative are considered, and extreme values of these are identified. These extremes are fit to a generalised extreme value distribution, and from this model return values (the expected magnitude of an observation within a given time window) are predicted. The causes of extreme values are investigated both in a case study, and also statistically by looking at contributions from geomagnetic storms, substorms, and sudden commencements. This work characterises the extreme part of the distribution of space weather effects on Ireland (and at similar latitudes), and hence examines those space weather observations which are likely to have the greatest impact on susceptible technologies.

At Jupiter, part of the auroral radio emissions are induced by the Galilean moons Io, Europa and Ganymede. Until now, except for Ganymede, they have been only remotely detected, using ground-based radio-telescopes or electric antennas aboard spacecraft. The polar trajectory of the Juno orbiter allows the spacecraft to cross the range of magnetic flux tubes which sustain the various Jupiter-satellite interactions, and in turn to sample in situ the associated radio emission regions. In this study, we focus on the detection and the characterization of radio sources associated with Io, Europa and Ganymede. Using electric wave measurements or radio observations (Juno/Waves), in situ electron measurements (Juno/JADE-E), and magnetic field measurements (Juno/MAG) we demonstrate that the Cyclotron Maser Instability (CMI) driven by a loss-cone electron distribution function is responsible for the encountered radio sources. We confirmed that radio emissions are associated with Main (MAW) or Reflected Alfvén Wing (RAW), but also show that for Europa and Ganymede, induced radio emissions are associated with Transhemispheric Electron Beam (TEB). For each traversed radio source, we determine the latitudinal extension, the CMI-resonant electron energy, and the bandwidth of the emission. We show that the presence of Alfvén perturbations and downward field aligned currents are necessary for the radio emissions to be amplified.

We define the spatial clustering of X-rays within Jupiter’s northern auroral regions by classifying their distributions into ‘X-ray auroral structures’. Using data from Chandra during Juno’s main mission observations (24 May 2016 – 8 September 2019), we define five X-ray structures based on their ionospheric location and calculate the distribution of auroral photons. The morphology and ionospheric location of these structures allow us to explore the possibility of numerous X-ray auroral magnetospheric drivers. We compare these distributions to Hubble Space Telescope (HST)and Juno (Waves and MAG) data, and a 1D solar wind propagation model to infer the state of Jupiter’s magnetosphere. Our results suggest that the five sub-classes of ‘X-ray structures’ fall under two broad morphologies: fully polar and low latitude emissions. Visibility modelling of each structure suggests the non-uniformity of the photon distributions across the Chandra intervals are likely associated with the switching on/off of magnetospheric drivers as opposed to geometrical effects. The combination of ultraviolet (UV) and X-ray morphological structures is a powerful tool to elucidate the behaviour of both electrons and ions and their link to solar wind/magnetospheric conditions in the absence of an upstream solar monitor.

To help understand and determine the driver of jovian auroral X-rays, we present the first statistical study to focus on the morphology and dynamics of the jovian northern hot spot (NHS) using Chandra data. The catalogue we explore dates from 18 December 2000 up to and including 8 September 2019. Using a numerical criterion, we characterize the typical and extreme behaviour of the concentrated NHS emissions across the catalogue. The mean power of the NHS is found to be 1.91 GW with a maximum brightness of 2.02 Rayleighs (R), representing by far the brightest parts of the jovian X-ray spectrum. We report a statistically significant region of emissions at the NHS center which is always present, the averaged hot spot nucleus (AHSNuc), with mean power of 0.57 GW and inferred average brightness of ∼ 1.2 R. We use a flux equivalence mapping model to link this distinct region of X-ray output to a likely source location and find that the majority of mappable NHS photons emanate from the pre-dusk to pre-midnight sector, coincident with the dusk flank boundary. A smaller cluster maps to the noon magnetopause boundary, dominated by the AHSNuc, suggesting that there may be multiple drivers of X-ray emissions. On application of timing analysis techniques (Rayleigh, Monte Carlo, Jackknife), we identify several instances of statistically significant quasi-periodic oscillations (QPOs) in the NHS photons ranging from ∼ 2.3-min to 36.4-min, suggesting possible links with ultra-low frequency activity on the magnetopause boundary (e.g. dayside reconnection, Kelvin-Helmholtz instabilities).

Auroral Kilometric Radiation (AKR) is radio emission that originates in particle acceleration regions along magnetic field lines, coinciding with discrete auroral arcs. Found in both hemispheres, an increase in the amplitude of a particular AKR source denotes the strengthening of parallel electric fields in the auroral zone, while the emission frequency gives insight into source region morphology. AKR viewing geometry is complex due to the confinement of the source regions to nightside local times and the anisotropy of the beaming pattern, so observations are highly dependent on spacecraft viewing position. We present a novel, empirical technique that selects AKR emission from remote radio observations made with the spin-axis aligned antenna of the Wind/WAVES instrument, based on the rapidly varying amplitude of AKR across spacecraft spin timescales. This selection is applied to 30 days of data in 1999, during which the Cassini spacecraft flew close to Earth and recorded AKR for the majority of the period, while the Wind spacecraft completed close to two, precessing petal orbits. We examine the flux density and integrated power, which gives an occurrence distribution with spacecraft local time that is typical of AKR, with an increase in power of around $10^{3}$ Wsr$^{-1}$ between dayside and nightside observations. We also find a statistically significant ($p < 10^{-5}$), previously observed diurnal modulation of the AKR integrated power for the period, further verifying the empirical selection of AKR and showing the promise of its application to larger subsets of Wind/WAVES observations.

On October 28th 2021 the Sun released a large Coronal Mass Ejection (CME) in Earth’s direction. An X1.0 class solar flare and a rare ground level enhancement (GLE) were observed, along with bright solar radio bursts. Here we examine data from the near-Earth environment to investigate the terrestrial response to this solar event, as a typical example of Sun-Earth interactions. The CME arrival is tracked at $\sim$1 AU from Wind radio observations and the interplanetary magnetic field (IMF) and solar wind dynamic pressure by \textit{in-situ} measurements of OMNI spacecraft. Geomagnetic activity is studied with indices including SYM-H while the auroral response is monitored by remote Wind radio measurements of Auroral Kilometric Radiation (AKR) and SSUSI UV observations. We quantify the timeline for solar wind-magnetosphere coupling via exploration of the dayside reconnection rate and polar cap voltages and address the visibility of AKR sources for a dayside radio observatory.

Magnetic reconnection is a fundamental physical process in planetary magnetospheres, in which plasma can be exchanged between the solar wind and a planetary magnetosphere, and material can be disconnected and ultimately lost from a magnetosphere. Magnetic reconnection in a planetary magnetotail can result in the release of plasmoids downtail and dipolarizations planetward of an x-line. The signatures of these products include characteristic deflections in the north-south component of the magnetic field which can be detected by in-situ spacecraft. These signatures have been identified by eye, semi-automated algorithms, and recently machine learning methods. Here, we apply statistical analysis to the most thorough catalogue of Kronian magnetospheric reconnection signatures created through machine learning methods to improve understanding of magnetospheric evolution. This research concludes that no quasi-steady position of the magnetotail x-line exists within 70 R S. This research introduces prediction equations to estimate the distribution of duration of plasmoid passage over the spacecraft (N = 300∆t −1.3 , bin width = 1 min) and north-south field deflection (N = 52∆B −2.1 θ , bin width = 0.25 nT) expected to be identified by an orbiting spacecraft across a year of observations. Furthermore, this research finds a local time asymmetry for reconnection identifications, with a preference for dusk-side over dawn-side. This may indicate a preference for Vasyliunas style reconnection over Dungey style for Saturn. Finally, through these distributions, the reconnection rate of Saturn’s magnetotail can be estimated as 3.22 reconnection events per day, with a resulting maximum mass loss from plasmoids of 34.4 kg s −1 on average, which is comparable with the magnetospheric mass loading from Enceladus (8-250 kg s −1).

We study 10 years (1995-2004 inclusive) of auroral kilometric radiation (AKR) radio emission data from the Wind spacecraft to examine the link between AKR and terrestrial substorms. We use substorm lists based on parameters including ground magnetometer signatures and geosynchronous particle injections as a basis for superposed epoch analyses of the AKR data. The results for each list show a similar, clear response of the AKR power around substorm onset. For nearly all event lists, the average response shows that the AKR power begins to increase around 20 minutes prior to expansion phase onset, as defined by the respective lists. The analysis of the spectral parameters of AKR bursts show that this increase in power is due to an extension of the source region to higher altitudes, which also precedes expansion phase onset by 20 minutes. Our observations show that the minimum frequency channel that observes AKR at this time, on average, is 60 kHz. AKR visibility is highly sensitive to observing spacecraft location, and the biggest radio response to substorm onset is seen in the 2100 - 0300 hr LT sector.

We present a statistical study of Jupiter’s disk X-ray emissions using 19 years of Chandra X-Ray Observatory (CXO) observations. Previous work has suggested that these emissions are consistent with solar X-rays elastically scattered from Jupiter’s upper atmosphere. We showcase a new Pulse Invariant (PI) filtering method that minimises instrumental effects which may produce unphysical trends in photon counts across the nearly-two-decade span of the observations. We compare the CXO results with solar X-ray flux data from the Geostationary Operational Environmental Satellites (GOES) X-ray Sensor (XRS) for the wavelength band 1-8 Å (long channel), to quantify the correlation between solar activity and jovian disk counts. We find a statistically significant Pearson’s Correlation Coefficient (PCC) of 0.9, which confirms that emitted jovian disk X-rays are predominantly governed by solar activity. We also utilise the high spatial resolution of the High Resolution Camera Instrument (HRC-I) on board the CXO to map the disk photons to their positions on Jupiter’s surface. Voronoi tessellation diagrams were constructed with the JRM09 (Juno Reference Model through Perijove 9) internal field model overlaid to identify any spatial preference of equatorial photons. After accounting for area and scattering across the curved surface of the planet, we find a preference of jovian disk emission at 2-3.5 Gauss surface magnetic field strength. This suggests that a portion of the disk X-rays may be linked to processes other than solar scattering: the spatial preference associated with magnetic field strength may imply increased precipitation from the radiation belts, as previously postulated.