Space Physics

This paper presents results on an investigation on storm time variation of Earth's magnetic field along the African geomagnetic equator during the recovery phases of the 5 th July 2011 and 16 th July 2012 geomagnetic storms. Magnetic field measurements were obtained from the International Real

A construction of the real 4D Minkowski space-time starting from quantum harmonic oscillators is proposed. First, a 2D spinor space and its dual are derived from the standard commutation relations obeyed by the ladder operators of two independent 1D harmonic oscillators. The complex 4D Minkowski vector space V is then constructed from these spinor space. The flat, real 4D Minkowski manifold is finally built as an approximate description of a manifold of unitary operators constructed from V . Lorentz invariance is recovered and several possible extensions are discussed, which connections to quantum optics and condensed matter physics.

Displacement waveforms derived from Global Navigation Satellite System (GNSS) data have become more commonly used by seismologists in the past 15 yrs. Unlike strong-motion accelerometer recordings that are affected by baseline offsets during very strong shaking, GNSS data record displacement with fidelity down to 0 Hz. Unfortunately, fully processed GNSS waveform data are still scarce because of limited public availability and the highly technical nature of GNSS processing. In an effort to further the use and adoption of high-rate (HR) GNSS for earthquake seismology, ground-motion studies, and structural monitoring applications, we describe and make available a database of fully curated HR-GNSS displacement waveforms for significant earthquakes. We include data from HR-GNSS networks at near-source to regional distances (1-1000 km) for 29 earthquakes between M w 6.0 and 9.0 worldwide. As a demonstration of the utility of this dataset, we model the magnitude scaling properties of peak ground displacements (PGDs) for these events. In addition to tripling the number of earthquakes used in previous PGD scaling studies, the number of data points over a range of distances and magnitudes is dramatically increased. The data are made available as a compressed archive with the article.

During the last few years, the amount of space debris has been frequently mentioned as a potential risk to current and future space operations. The purpose of this article was to describe the discussions held at the First Sustainable Space Economy Workshop held in Finland 2019. The workshop gathered together experts with economic, legal, regulatory, technological, and environmental backgrounds, with an aim of discussing the sustainable use of space from all these perspectives. As an outcome of these discussions, we find that two concepts, satellite sustainability footprint and orbital capacity, should be introduced at an international level. The satellite sustainability footprint measures how likely the satellite stays healthy and operating, without causing risks to self or others. The orbit capacity is essentially an integral of the footprint over an orbit, and it determines how many satellites of different footprints could be launched to the same orbit. In addition, in this article, we discuss how to realize such concepts within the current normative framework. The authors suggest both top-down and bottom-up approaches, necessitating negotiations within an intergovernmental framework and with the relevant space actors. The most important finding of the workshop and this article, however, is that different space-related fields and experts having diverse backgrounds should continuously discuss in a constructive and informal manner to realize the sustainable utilization of space in practice.

We study the effects of oblateness up to J 4 of the primaries and power-law density profile (PDP) on the linear stability of libration location of an infinitesimal mass within the framework of restricted three body problem (R3BP), by using a more realistic model in which a disc with PDP is rotating around the common center of the system mass with perturbed mean motion. The existence and stability of triangular equilibrium points have been explored. It has been shown that triangular equilibrium points are stable for 0 < µ < µ c and unstable for µ c ≤ µ ≤ 1/2, where µ c denotes the critical mass parameter. We find that, the oblateness up to J 2 of the primaries and the radiation reduces the stability range while the oblateness up to J 4 of the primaries increases the size of stability both in the context where PDP is considered and ignored. The PDP has an effect of about ≈ 0.01 reduction on the application of µ c to Earth-Moon and Jupiter-Moons systems. We find that the comprehensive effects of the perturbations have a stabilizing proclivity. However, the oblateness up to J 2 of the primaries and the radiation of the primaries have tendency for instability, while coefficients up to J 4 of the primaries have stability predisposition. In the limiting case c = 0, and also by setting appropriate parameter(s) to zero, our results are in excellent agreement with the ones obtained previously. Libration points play a very important role in space mission and as a consequence, our results have a practical application

We present statistical results for the analysis of 240 Auroral Kilometric Radiation (AKR) dynamical spectra containing 3,750 short-time AKR bursts each, and recorded on-board Interball-2 mission (POLRAD and MEMO experiments). Data were collected between December 1996 and February 1998. We found that frequency distribution of short AKR bursts as a function of their Power Spectral Density, shows for intense bursts a powerlaw fall. This is the hallmark of the Self-Organized Criticality (SOC) systems. In our case a simple analytical Logistic Growth SOC model can reproduce increments of Electron Cyclotron Maser instability expected for AKR.

This article posits that solar sunspot variability perturbs Van Allen Belt particle fluxes, driving climate impacts via atmospheric angular momentum (AAM)-mediated lengthof-day (LOD) shifts. Anchored in solar-terrestrial physics, we quantify this cascadesolar wind to ionosphere to ocean currents-and frame Earth as a tempered analog to Mars' solar-driven atmospheric collapse. Contrasting it with rival mechanisms, we propose interdisciplinary tests to disentangle solar and anthropogenic climate forcings, offering a robust hypothesis after a decade of refinement.

Auroral Kilometric Radiation (AKR) is the most powerful radio emission from planetary magnetospheres, and is a important probe of the plasma environment of the inner magnetosphere. Recent Cluster-based studies of terrestrial AKR, and Cassini studies of Jovian decametric (DAM) and Saturnian kilometric radiation (SKR) highlight many similarities, but also significant differences. While the basic radiation emission mechanism (cyclotron maser instability) appears to be common to all three planetary systems, the unique physical environment of each system results in very different observed properties. For example, the longitudinal distribution of AKR sources on the three systems is quite different, probably a result of the differing geometry of solar wind penetration into the respective magnetospheres. Likewise, the angular beaming pattern of AKR, although narrow in all three cases, may be modified by the local plasma cavity geometry at the AKR sources and/or differing electron velocity distributions (loss-cone vs. shell). Fine-scale drifting frequency structures (SAKR on Earth, S-bursts on Jupiter and Saturn) have been interpreted as evidence of upward-traveling ion solitary waves on Earth, but may be a result of trapped Alfven waves on Jupiter. The variation in observed AKR properties in our solar system allows an informed guess at scaling laws for AKR emission with planetary magnetic moment and distance from the parent star, which can inform searches for AKR emission from extra-solar planets.

The large-scale observational capabilities of distributed instrumentation fielded by amateur radio operators and radio science enthusiasts offers tremendous opportunity for advancement in the fields of heliophysics, radio science, and space weather forecasting and operations. Well-established amateur radio networks such as the RBN, WSPRNet, and PSKReporter already provide a rich, ever-growing long-term dataset of bottomside ionospheric observations. Conversely, up-and-coming purpose-built citizen science networks, and the associated novel instruments, offer opportunities for citizen scientists, professional researchers, and industry to field instrument networks optimized to make measurements targeting specific science questions and operational needs. When these measurements are used in conjunction with existing networks of professional instrumentation, the potential for discovery becomes even greater.

Except for a brief mention at the beginning, the paper deals with the technical and legal aspects of space exploration and, to a lesser extent, the energy sources used in the conquest of space. The idea of energy from space is not new. As early as 1923, Konstantin Tsiolkovsky envisioned a system based on mirrors placed in space to send amplified sunbeams back to Earth. A bit later, in 1941, the famous science fiction writer Isaac Asimov came up with a similar idea (ESA 2022a), and in 1975, the physicist Gerard K. O'Neill took the idea one step further, bringing it even closer to the present day: he had already written that "manufacturing facilities in high orbit could be used to build satellite solar power stations from lunar materials" (O'Neill 1975: 943). If we look at the 20 th century space science fiction literature, we can see that the various ways of producing energy that appeared in novels, which seemed impossible and futuristic at the time, are beginning to materialise, or are already partially operational. It might be worth picking up today's science fiction literature to get a more accurate picture of our own future. This paper has a similar goal: to show what kind of energy production and supply opportunities will exist during the exploration and eventual colonisation of space at different locations and distances.

The American Physical Society Orientation of x-lines in asymmetric magnetic reconnection YI-HSIN LIU, MICHAEL HESSE, MASHA KUZNETSOVA, NASA/GSFC -At Earth's magnetopause, reconnection proceeds asymmetrically between magnetosheath plasmas, namely solar wind plasmas compressed by Earth's bow shock, and magnetospheric plasmas. In an asymmetric configuration, it is unclear if there is a simple principle to determine the orientation of the x-line. Using fully kinetic simulations, we study this issue and a spatially localized perturbation is employed to induce a single x-line, that has sufficient freedom to choose its orientation in threedimensional systems. The effect of ion to electron mass ratio is investigated, and the x-line appears to bisect the magnetic shear angle across the current sheet in the large mass ratio limit. The deviation from the bisection angle in the lower mass ratio limit can be explained by the physics of tearing instability. 1 The local physics control of the x-line orientation studied in this slab geometry could potentially interplay with global geometrical effects to determine the location of collisionless magnetic reconnection at Earth's magnetopause.

Several contributions of the Thrace group to magnetospheric, solar, and planetary physics over the last three decades are summarized from the perspective of a paradigm shift in nonlinear plasma physics. The work by Dennis Papadopoulos on plasma instabilities has been a source of inspiration for our magnetospheric studies including the introduction of the chaos hypothesis.

It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, TEC modelling was performed over Sutherland (32.38∘ S, 20.81∘ E, 41.09∘ S geomagnetic), South Africa, during storm conditions, using a combination of empirical orthogonal function (EOF) and regression analyses techniques. The neural network (NN) technique was also applied to the same TEC data set, and its output was compared with TEC modeled using the EOF model. TEC was derived from GPS observations, and a geomagnetic storm was defined for Dst ≤ −50 nT. The hour of the day and the day number of the year, F10.7p and A indices, were chosen as inputs for the modeling techniques
to take into account diurnal and seasonal variation of TEC, solar, and geomagnetic activities, respectively. Both EOF and NN models were developed using GPS TEC data for storm days counted from 1999 to 2013
and tested on different storms. For interpolation, the EOF and NN models were validated on storms that occurred during high and low solar activity periods (storms of 2000 and 2006), while for extrapolation the validation was done for the storms of 2014 and 2015, identified based on the provisional Dst index data. A comparison of the modeled TEC with the observed TEC showed that both EOF and NN models perform well for storms with non-significant ionospheric TEC response and storms that occurred during period of low solar activity. For storms with significant TEC response, TEC magnitude is well captured during the nighttime and early morning, but short-term features, TEC enhancement, and depression are not sufficiently captured by the models. Statistically, the NN model performs 12.79% better than the EOF model on average, over all storm periods considered. Furthermore, it has been shown that the EOF and NN models developed for
a specific station can be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7∘ and 10.6∘ , respectively. This is an important result as it reduces the data dimensionality problem for computational purposes.

There have been many significant advances in understanding magnetic field reconnection as a result of improved space measurements and two-dimensional computer simulations. While reviews of recent work have tended to focus on symmetric reconnection on ion and larger spatial scales, the present review will focus on asymmetric reconnection and on electron scale physics involving the reconnection site, parallel electric fields, and electron acceleration.

We present the study of one of the first magnetopause crossings observed by the four Cluster spacecraft simultaneously, on 10 December 2000. Although the delays between the crossings are very short, the features of the boundary appear quite different as seen by the different spacecraft, strongly suggesting the presence of a local curvature of the magnetopause at that time. The small-scale fluctuations observed by the STAFF search-coil experiment are placed in relation to this context. A preliminary investigation of their behaviour on the boundary and in the neighbourhood magnetosheath is performed in comparison with the theoretical model of Belmont and Rezeau (2001), which describes the interaction of waves with the boundary.

Future in situ space plasma investigations will likely involve spatially distributed observatories comprised of multiple spacecraft, beyond the four and five spacecraft configurations currently in operation. Inferring the magnetic field structure across the observatory, and not simply at the observation points, is a necessary step towards characterizing fundamental plasma processes using these unique multi-point, multi-scale data sets. We propose improvements upon the classic first-order reconstruction method, as well as a second-order method, utilizing magnetometer measurements from a realistic nine-spacecraft observatory. The improved first-order method, which averages over select ensembles of four spacecraft, reconstructs the magnetic field associated with simple current sheets and numerical simulations of turbulence accurately over larger volumes compared to second-order methods or first-order methods using a single regular tetrahedron. Using this averaging method on data sets w...

This White Paper outlines the importance of addressing the fundamental science theme "How are charged particles energized in space plasmas" through a future ESA mission. The White Paper presents five compelling science questions related to particle energization by shocks, reconnection, waves and turbulence, jets and their combinations. Answering these questions requires resolving scale coupling, nonlinearity, and nonstationarity, which cannot be done with existing multi-point observations. In situ measurements from a multi-point, multi-scale L-class Plasma Observatory consisting of at least seven spacecraft covering fluid, ion, and electron scales are needed. The Plasma Observatory will enable a paradigm shift in our comprehension of particle energization and space plasma physics in general, with a very important impact on solar and astrophysical plasmas. It will be the next logical step following Cluster, THEMIS, and MMS for the very large and active European space plasmas community. Being one of the cornerstone missions of the future ESA Voyage 2050 science programme, it would further strengthen the European scientific and technical leadership in this important field.

Extraction of knowledge from massive and complex data sets generated from peta-scale simulations poses a major obstacle to scientific progress. We propose a new approach to solving this problem by utilizing an innovative feature extraction technique in combination with specialized data mining algorithms which can be incorporated as part of the scientific visualization pipeline. In this paper we show how data from simulations as well as many other real life examples can be represented in a form of multivariate time series. Accordingly, we have adapted a multivariate time series analysis data mining technique to handle simulation data. The technique extracts global features and metafeatures in the 2D simulation dataset in order to capture the necessary time-lapse information. The features are then used to create a static, intermediate data set that is suitable for analysis using the standard supervised data mining techniques. The viability of the new algorithm called MineTool-M is dem...

this booklet is produced within the Gfg 2 project, a three year coordination action, funded by the 7th Framework Program of the European Commission under the Environment theme. Its mission is to better assess the value of Global Navigational Satellite Systems (GNSS) for Global Environmental Earth Observation (GEEO) and GEOSS.

Various physical processes in association with magnetic reconnection occur over multiple scales from the microscopic to macroscopic scale lengths. This paper reviews multi-scale and cross-scale aspects of magnetic reconnection revealed in the near-Earth space beyond the general global-scale features and magnetospheric circulation organized by the Dungey Cycle. Significant and novel advancements recently reported, in particular, since the launch of the Magnetospheric Multi-scale mission (MMS), are highlighted being categorized into different locations with different magnetic topologies. These potentially paradigm-shifting findings include shock and foreshock transient driven reconnection, magnetosheath turbulent reconnection, flow shear driven reconnection, multiple X-line structures generated in the dayside/flankside/nightside magnetospheric current sheets, development and evolution of reconnection-driven structures such as flux transfer events, flux ropes, and dipolarization fronts...

Recent observations in the Earth's magnetotail have shown rapid increases in the fluxes of energetic electrons with energies up to 100's of keV associated with dipolarization fronts that propagate into the inner magnetosphere. On August 15, 2001 the four Cluster spacecraft located slightly dawnward of midnight (yGSM----5.4RE) at xGSM--1$RE observed a series of earthward propagating dipolarization fronts [Hwang et al., 2010]. At least 6 dipolarization fronts were observed in a 20m interval. Unlike previously reported cases the fluxes of electrons up to 95keV decreased during the passage of the first three fronts over the spacecraft. The energetic electron fluxes increased during the passage of the last three fronts. We have performed a global magnetohydrodynamic simulation of this event using solar wind observations from the ACE satellite to drive the simulation. In the simulation a very complex reconnection system in the near-Earth tail at XGSM--20RE launched a series of earthward propagating dipolarization fronts that are similar to those observed on Cluster. The simulation results indicate that the Cluster spacecraft were just earthward of the reconnection site. In this paper we will present a study of the dynamics of electrons associated with these events by using the large-scale kinetic simulation approach in which we launch a large number of electrons into the electric and magnetic fields from this simulation.

Solar wind magnetometer and plasma data and magnetometer data acquired by Cluster in the magnetospheric plasma sheet are employed to construct probability distribution functions (PDFs) of velocity fluctuations and magnetic field fluctuations over various temporal and spatial scales. This technique, often used in analysis of laboratory plasmas, is used to look for intermittent plasma turbulence. We examined the distribution of the magnetic field and plasma fluctuations for a single spacecraft, and between pairs of highly correlated spacecraft time series data in both the plasma sheet and the solar wind (fast and slow speed streams). We demonstrate that the plasma sheet fluctuations are multi-fractal and do not rescale to a single master curve. The plasma and magnetic field PDFs are fit with the Castaing et al. [1990] energy cascade model. This model is able to capture the non-Gaussian behavior at small temporal and spatial separations in the wings of the distribution and non-self sim...

The Rosetta Plasma Consortium (RPC) will make in-situ measurements of the plasma environment of comet 67P/Churyumov-Gerasimenko. The consortium will provide the complementary data sets necessary for an understanding of the plasma processes in the inner coma, and the structure and evolution of the coma with the increasing cometary activity. Five sensors have been selected to achieve this: the Ion and Electron Sensor (IES), the Ion Composition Analyser (ICA), the Langmuir Probe (LAP), the Mutual Impedance Probe (MIP) and the Magnetometer (MAG). The sensors interface to the spacecraft through the Plasma Interface Unit (PIU). The consortium approach allows for scientific, technical and operational coordination, and makes optimum use of the available mass and power resources.

Launched on an elliptical high inclination orbit (apogee: 19.6 R E ) since January 2001 the Cluster satellites have been conducting the first detailed three-dimensional studies of the high-latitude dayside magnetosphere, including the exterior cusp, neighboring boundary layers and magnetopause regions. Cluster satellites carry the CIS ion spectrometers that provide high-precision, 3D distributions of low-energy (< 35 keV/e) ions every 4 s. This paper presents the first two observations of the cusp and/or magnetopause behaviour made under different interplanetary magnetic field (IMF) conditions. Flow directions, 3D distribution functions, density profiles and ion composition profiles are analyzed to demonstrate the high variability of high-latitude regions. In the first crossing analyzed (26 January 2001, dusk side, IMF-B Z < 0), multiple, isolated boundary layer, magnetopause and magnetosheath encounters clearly occurred on a quasi-steady basis for ∼ 2 hours. CIS ion instruments show systematic accelerated flows in the current layer and adjacent boundary layers on the Earthward side of the magnetopause. Multi-point analysis of the magnetopause, combining magnetic and plasma data from the four Cluster spacecraft, demonstrates that oscillatory outward-inward motions occur with a normal speed of the order of ± 40 km/s; the thickness of the high-latitude current layer is evaluated to be of the order of 900-1000 km. Alfvénic accelerated flows and D-shaped distributions are convincing signatures of a magnetic reconnection occurring equatorward of the Cluster satellites. Moreover, the internal magnetic and plasma structure of a flux transfer event (FTE) is analyzed in detail; its size along the magnetopause surface is ∼ 12 000 km and it

Magnetic field measurements from the four Cluster spacecraft from the mid-and high-altitude cusp are presented. Cluster underwent two encounters with the midaltitude cusp during its commissioning phase (24 August 2000). Evidence for field-aligned currents (FACs) was seen in the data from all three operating spacecraft from northern and southern cusps. The extent of the FACs was of the order of 1 R E in the X-direction, and at least 300 km in the Y -direction. However, fine-scale field structures with scales of the order of the spacecraft separation (300 km) were observed within the FACs. In the northern crossing, two of the spacecraft appeared to lie along the same magnetic field line, and observed very well matched signals. However, the third spacecraft showed evidence for structuring transverse to the field on scales of a few hundred km. A crossing of the highaltitude cusp from 13 February 2001 is presented. It is revealed to be a highly dynamic structure with the boundaries moving with velocities ranging from a few km/s to tens of km/s, and having structure on timescales ranging from less than one minute up to several minutes. The cusp proper is associated with the presence of a very disordered magnetic field, which is entirely different from the magnetosheath turbulence.

Solar energetic particle events produced by the flare reconnection process are impulsive and short live in nature. Both the shock and waves are expected occur during energy solar eruption; therefore, it might be possible that the observed SEPs are due to combine effect of these two processes. CMEs associated with SEPs generally originate from solar active region. Active region can store and release vast amount of magnetic energy. During the solar maximum phase, majority of SEP events may occur, so it is difficult to identify the source region of CMEs (Gopalswamy N., 2009). In the rising phase of any solar cycle, SEP events are less, thus one get more chance to study SEP event and can detect their source region.

Conventional thinking says the universe is infinite. But it could be finite and relatively small, merely giving the illusion of a greater one, like a hall of mirrors. Recent astronomical measurements add support to a finite space with a dodecahedral topology.

This study presents new observations of fine structure and motion of the bow shock formed in the solar wind, upstream of the Earth's magnetosphere. NASA's Magnetospheric Multiscale (MMS) mission has recorded data during 11 encounters with a shock oscillating with frequency of 1 mHz. Shocks move with a speed of 4-17 km s -1 ; have thickness of 100 km, i.e. an ion gyroradius; and represent cascades of compressional magnetic field and plasma density structures of increasing frequencies or smaller spatial scales. Induced density gradients initiate chains of cross-field current-driven instabilities that heat solar wind ions by the stochastic E × B wave energisation mechanism. The theoretical ion energisation limits are confirmed by observations. We have identified the ion acceleration mechanism operating at shocks and explained double-beam structures in the velocity space. The nature of this mechanism has been revealed as a stochastic resonant acceleration (SRA). The results provide for the first time a consistent picture of a chain of plasma processes that generate collisionless shocks and are responsible for particle energisation.

This project focuses on the comprehensive design and analysis of a spring mechanism for a P-Pod deployer using a combination of MATLAB, SolidWorks, and ANSYS. Initially, MATLAB was employed to perform critical calculations, including determining the number of coils, wire diameter, coil diameter, and the stiffness constant of the spring. These parameters were optimized to meet the specific load and deflection requirements of the P-Pod deployer. Following the computational design phase, SolidWorks was utilized to create a detailed 3D CAD model of the spring. This model incorporated the precise geometric and material specifications derived from the MATLAB calculations. Subsequently, the CAD model was imported into ANSYS for finite element analysis (FEA) to evaluate the spring's performance under operational loads, with a particular focus on buckling behavior. The FEA provided insights into the stress distribution, deformation, and factor of safety, ensuring the spring's reliability and effectiveness in the deployer mechanism. Iterative design adjustments were made based on the ANSYS results to achieve an optimal and robust spring design. The integration of MATLAB, SolidWorks, and ANSYS facilitated a thorough and efficient design process, culminating in a spring mechanism that meets the stringent requirements of the P-Pod deployer application.

The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single-and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

This paper introduces ISEE_3D, an interactive visualization tool for three-dimensional plasma velocity distribution functions, developed by the Institute for Space-Earth Environmental Research, Nagoya University, Japan. The tool provides a variety of methods to visualize the distribution function of space plasma: scatter, volume, and isosurface modes. The tool also has a wide range of functions, such as displaying magnetic field vectors and two-dimensional slices of distributions to facilitate extensive analysis. The coordinate transformation to the magnetic field coordinates is also implemented in the tool. The source codes of the tool are written as scripts of a widely used data analysis software language, Interactive Data Language, which has been widespread in the field of space physics and solar physics. The current version of the tool can be used for data files of the plasma distribution function from the Geotail satellite mission, which are publicly accessible through the Data Archives and Transmission System of the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace Exploration Agency (JAXA). The tool is also available in the Space Physics Environment Data Analysis Software to visualize plasma data from the Magnetospheric Multiscale and the Time History of Events and Macroscale Interactions during Substorms missions. The tool is planned to be applied to data from other missions, such as Arase (ERG) and Van Allen Probes after replacing or adding data loading plug-ins. This visualization tool helps scientists understand the dynamics of space plasma better, particularly in the regions where the magnetohydrodynamic approximation is not valid, for example, the Earth's inner magnetosphere, magnetopause, bow shock, and plasma sheet.

The fields of solar radiophysics and solar system radio physics, or radio heliophysics, will benefit immensely from an instrument with the capabilities projected for SKA. Potential applications include interplanetary scintillation (IPS), radio-burst tracking, and solar spectral radio imaging with a superior sensitivity. These will provide breakthrough new insights and results in topics of fundamental importance, such as the physics of impulsive energy releases, magnetohydrodynamic oscillations and turbulence, the dynamics of post-eruptive processes, energetic particle acceleration, the structure of the solar wind and the development and evolution of solar wind transients at distances up to and beyond the orbit of the Earth. The combination of the high spectral, time and spatial resolution and the unprecedented sensitivity of the SKA will radically advance our understanding of basic physical processes operating in solar and heliospheric plasmas and provide a solid foundation for the forecasting of space weather events.

"Galileo Galilei" (GG) is a small satellite designed to fly in low Earth orbit with the goal of testing the Equivalence Principle-which is at the basis of the General Theory of Relativity-to 1 part in 10 17. If successful, it would improve current laboratory results by 4 orders of magnitude. A confirmation would strongly constrain theories; proof of violation is believed to lead to a scientific revolution. The experiment design allows it to be carried out at ambient temperature inside a small 1-axis stabilized satellite (250 kg total mass). GG is under investigation at Phase A-2 level by ASI (Agenzia Spaziale Italiana) at Thales Alenia Space in Torino, while a laboratory prototype (known as GGG) is operational at INFN laboratories in Pisa, supported by INFN (Istituto Nazionale di fisica Nucleare) and ASI. A final study report will be published in 2009.

This research explores sonification - the assigning a sound to a data stream - as a useful tool for space science data exploration. In this research the authors use the xSonify Java-based tool, developed to explore space data using sound, to analyze radio data at 20.1 MHz for the formation of irregularities in the ionosphere. The data was audified in real time, and the power spectra sonified to expose discrete resonances, combs and bands. Since our telescopes are relatively insensitive, a time series analysis will not reveal much about the ionosphere, but a frequency domain analysis, especially over a particular range, will reveal some very interesting features interpretable in terms of radio twinkling. Sonification lead the authors to notice changes at ionospheric recombination time (3Z) that were characterized using FFT algorithms.

Active ionospheric experiments using high-power, high-frequency transmitters, "heaters", to study plasma processes in the ionosphere and magnetosphere continue to provide new insights into understanding plasma and geophysical proceses. This review describes the heating facilities, past and present, and discusses scientific results from these facilities and associated space missions. Phenomena that have been observed with these facilities are reviewed along with theoretical explanations that have been proposed or are commonly accepted. Gaps or uncertainties in understanding of heating initiated phenomena are discussed together with proposed science questions to be addressed in the future. Suggestions for improvements and additions to existing facilities are presented including important satellite missions which are necessary to answer the outstanding questions in this field. Keywords. Active experiments. Ionospheric heating. HAARP. SURA. Arecibo. ULF waves. Ionospheric feedback instability. VLF waves. Ionospheric irregularities. Plasma instabilities. Wave-particle interactions. Artificial aurora. EISCAT. Ionosphere. DEMETER. Ionospheric resonator.

Relative dynamics of the radio sources of the metric type II burst with three emission lanes and coronal mass ejection (CME) occurred in the lower corona (r K 1:5R ) during the SOL2011-02-16T14:19 event is studied. The observational data of the Nancay Radioheliograph (NRH) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) are used. These observations are also supplemented by the data sets obtained with the STEREO-A and -B, RHESSI, and GOES spacecraft, as well as with the ground-based solar radio spectrometers. It is found that the sources of the radio burst were located ahead of the expanding CME and had a complex spatial structure. The first and the second lanes were both emitted from the "magnetic funnel" -a bundle of open magnetic field lines separated the south and north systems of magnetic loops of the active region. Due to the projection effect and limited angular resolution of the NRH it is not possible to determine, whether the spatial locations of the radio sources of the two first emission lanes differed or not. It is argued that the observations support the hypothesis that the radio sources of the first and second lanes could be emitted respectively ahead of and behind a front of the same weak (the Alfve ´n Mach number M A % 1:1-1:2), fast mode, quasi-parallel piston MHD shock wave. However, the third lane of the burst was definitely emitted from a different place. Its radio sources were situated ahead of the north-west part of the CME propagated through the north system of magnetic loops. This indicates clearly that different emission lanes of the same type II burst can be a result of propagation of different parts of a single CME through regions with different physical conditions (geometries and plasma densities) in the lower corona.

On May 10, 2024, a severe geomagnetic storm coinciding with Mother’s Day in Mexico lasted over 40 hours and produced polar auroras observable at low latitudes. This storm, the most intense since 2003, resulted from a series of solar flares and coronal mass ejections from active region 3664. The event was significant for space weather studies in Mexico, marking a milestone by enabling comprehensive measurements of its effects. The Mexico Space Weather Service (SCIESMEX) and the National Space Weather Laboratory (LANCE) had prepared for such an event since their inception. LANCE’s instrument networks recorded solar chromospheric images, solar radio bursts, geomagnetic variations, Schumann resonances, ionospheric disturbances, and energetic particle flows. They also monitored Geomagnetically Induced Currents (GICs) in four strategic substations of the national electrical system. This provided unprecedented insights into the dynamics of severe space weather events at the North-American low-latitude environment. Citizen science efforts documented auroras and regional responses, capturing variations in geomagnetic indices, ionospheric disturbances, cosmic ray fluxes, GICs, and technological impacts. SCIESMEX worked with the National Civil Protection System (SINAPROC) to issue warnings, ensuring public awareness and preparedness. This coordination underscores the importance of effective communication and collaboration in mitigating impacts. The May 2024 geomagnetic storm demonstrated the critical role of preparedness, research, and public education in reducing the effects of future space weather events in Mexico.

In September 1859 the Colaba observatory measured the most extreme geomagnetic disturbance ever recorded at low latitudes related to solar activity: the Carrington storm. This paper describes a geomagnetic disturbance case with a profile extraordinarily similar to the disturbance of the Carrington event at Colaba: the event on 29 October 2003 at Tihany magnetic observatory in Hungary. The analysis of the H-field at different locations during the ''Carrington-like'' event leads to a re-interpretation of the 1859 event. The major conclusions of the paper are the following: (a) the global Dst or SYM-H, as indices based on averaging, missed the largest geomagnetic disturbance in the 29 October 2003 event and might have missed the 1859 disturbance, since the large spike in the horizontal component (H) of terrestrial magnetic field depends strongly on magnetic local time (MLT); (b) the main cause of the large drop in H recorded at Colaba during the Carrington storm was not the ring current but field-aligned currents (FACs); and (c) the very local signatures of the H-spike imply that a Carrington-like event can occur more often than expected.

A study of the evolution of Kristian Birkeland's theories of cosmical physics is presented, with special reference to his laboratory gas-discharge experiments. It is found that his most important thoughts were molded from an intense cross-fertilization between laboratory experiments, geophysical observations and mathematical modelling. Occasionally, original ideas of fundamental importance in the cosmic context emerged from unexpected laboratory results. Possible implications for a sound cross-dikciplinary approach to modern plasma science are discussed.

During the last few years, the amount of space debris has been frequently mentioned as a potential risk to current and future space operations. The purpose of this article was to describe the discussions held at the First Sustainable Space Economy Workshop held in Finland 2019. The workshop gathered together experts with economic, legal, regulatory, technological, and environmental backgrounds, with an aim of discussing the sustainable use of space from all these perspectives. As an outcome of these discussions, we find that two concepts, satellite sustainability footprint and orbital capacity, should be introduced at an international level. The satellite sustainability footprint measures how likely the satellite stays healthy and operating, without causing risks to self or others. The orbit capacity is essentially an integral of the footprint over an orbit, and it determines how many satellites of different footprints could be launched to the same orbit. In addition, in this article, we discuss how to realize such concepts within the current normative framework. The authors suggest both top-down and bottom-up approaches, necessitating negotiations within an intergovernmental framework and with the relevant space actors. The most important finding of the workshop and this article, however, is that different space-related fields and experts having diverse backgrounds should continuously discuss in a constructive and informal manner to realize the sustainable utilization of space in practice.