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The study of Electro Magnetic Ion Cyclotron (EMIC) wave-induced electron precipitation has a legacy in early work suggesting EMIC waves could precipitate relativistic electrons. As such, EMIC waves represent a significant loss process for the Outer Radiation Belt, and deposit high energy electron precipitation flux deep into the atmosphere. Here we present an analysis of an example of EMIC-induced electron precipitation observed by two satellites in Low Earth Orbit, combined with EMIC wave signatures in ground-based magnetometers in Finland, and Antarctica. Electron precipitation spectral information is provided by satellite data which considers the energy range of scattered electrons during the potential EMIC wave event. We investigate the high energy resolution DEMETER IDP electron measurements in the 80keV - 2MeV range, when the detector was looking into the bounce-loss-cone, i.e., flying over the North Atlantic region.In order to assess the effect of potential proton precipitation contamination of the IDP detector we use nearby POES proton flux measurements, compensating for the IDP protective aluminium foil through a calculation of the attenuation of the proton spectrum using the integrated MULASSIS transport code. Our results are considered in the context of recent work indicating a wide energy range of non-relativistic electron precipitation is present in EMIC-induced precipitation in addition to the relativistic energy electrons suggested from the original theoretical suggestions. Our confirmation of non-relativistic energy ranges in EMIC-induced precipitation events supports the atmospheric chemical modelling analysis undertaken recently which showed that EMIC-induced precipitation is capable of causing notable composition changes., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

In February 2007, the STEREO‐B spacecraft encountered the magnetosheath, plasma sheet and plasma sheet boundary layer from about 200 RE to 300 RE downtail. This time period was during solar minimum, and there was no storm activity during this month. Using data from the PLASTIC instrument, we find that even during quiet times, O+ is a constant feature of the deep magnetotail, with an O+ density of about 15% of the O+ density in the near‐earth plasma sheet for similar conditions. The tailward flux of the O+ is similar to the flux of O+ beams that have been observed in the lobe/mantle region of the deep tail. The total outflow rate of the O+ down the plasma sheet is 1.1 × 1024 ions/s, which is 10% of the total outflow rate of 1 × 1025 ions/s, and of the same order as the estimated loss from dayside transport.

We have studied the interaction of fast solar wind hydrogen atoms with the martian atmosphere by a three-dimensional Monte Carlo simulation. These energetic neutral hydrogen atoms, H-ENAs, are formed upstream of the martian bow shock. Both H-ENAs scattered and non-scattered from the martian atmosphere/exosphere were studied. The colliding H-ENAs were found to scatter both to the dayside and nightside. On the dayside they contribute to the so-called H-ENA albedo. On the nightside the heated and scattered hydrogen atoms were found also in the martian wake. The density, the energy distribution function and the direction of the velocity of H-ENAs on the nightside are presented. The present study describes a novel “ENA sounding” technique in which energetic neutral atoms are used to derive information of the properties of planetary exosphere and atmosphere in a similar manner as the solar wind photons are used to derive atmospheric densities by measuring the scattered UV light. A detailed study of the direction and energy of the scattered and non-scattered H-ENAs suggest that the ENA sounding is a method to study the interaction between the planetary atmosphere and the solar wind and to monitor the density, and likely also the magnetization, of the planetary upper atmosphere. Already present-day ENA instrument should be capable to detect the analyzed particle fluxes.

The ELectron Spectrometer (ELS) from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) flown on the Mars Express spacecraft has an 8% energy resolution, combined with the capability to oversample the martian electron distribution. This makes possible the resolution and identification of electrons generated as a result of the He 304 Å ionization of CO2 at the martian exobase on the dayside of the planet. Ionospheric photoelectrons were observed during almost every pass into the ionosphere and CO2 photoelectron peaks were identified near the terminator. Atmospherically generated CO2 photoelectrons are also observed at 10,000 km altitude in the martian tail near the inner magnetospheric boundary. Observations over a wide range of spacecraft orbits showed a consistent presence of photoelectrons at locations along the inner magnetospheric boundary and in the ionosphere, from an altitude of 250 to 10,000 km.

The Analyzer of Space Plasmas and Energetic Atoms (ASPERA‐4) instrument on Venus Express is used to determine bow shock position at Venus using ion data alone, using data recorded during a solar minimum from the Ion Mass Analyzer (IMA) which is part of the ASPERA‐4 package. Previous models constructed from solar minimum data using Venus Express, Pioneer Venus Orbiter (PVO) and Venera 9 and 10 are also compared to the current fit. An important feature of this new fit is a statistical accuracy introduced in the form of a probability weighting function for the data points, based on the time spent in particular locations. The bow shock curve is then compared to two‐dimensional ion maps. These verify the accuracy of this and previous solar minimum fit curves based on PVO and Venus Express magnetic data. Comparing all bow shock models to the 2D ion maps shows that a combination of models produces the best fit. Since all the fitted curves show differences in position they are investigated relative to the solar conditions pertaining at the times when the individual data sets were measured. The sub solar point and terminator distance were thus found to vary linearly with sunspot number and hence with solar activity. This relationship, which was already known to exist between solar maximum and solar minimum, is now shown to exist between different solar minima and even within the same minimum. This indicates a need for the mechanisms for bow shock maintenance and variance to be more closely modeled.

The Solar Orbiter mission seeks to make connections between the physical processes occurring at the Sun or in the solar corona and the nature of the solar wind created by those processes which is subsequently observed at the spacecraft. The mission also targets physical processes occurring in the solar wind itself during its journey from its source to the spacecraft. To meet the specific mission science goals, Solar Orbiter will be equipped with both remote-sensing and in-situ instruments which will make unprecedented measurements of the solar atmosphere and the inner heliosphere. A crucial set of measurements will be provided by the Solar Wind Analyser (SWA) suite of instruments. This suite consists of an Electron Analyser System (SWA-EAS), a Proton and Alpha particle Sensor (SWA-PAS), and a Heavy Ion Sensor (SWA-HIS) which are jointly served by a central control and data processing unit (SWA-DPU). Together these sensors will measure and categorise the vast majority of thermal and suprathermal ions and electrons in the solar wind and determine the abundances and charge states of the heavy ion populations. The three sensors in the SWA suite are each based on the top hat electrostatic analyser concept, which has been deployed on numerous space plasma missions. The SWA-EAS uses two such heads, each of which have 360◦ azimuth acceptance angles and ±45◦ aperture deflection plates. Together these two sensors, which are mounted on the end of the boom, will cover a full sky field-of-view (FoV) (except for blockages by the spacecraft and its appendages) and measure the full 3D velocity distribution function (VDF) of solar wind electrons in the energy range of a few eV to ∼5 keV. The SWA-PAS instrument also uses an electrostatic analyser with a more confined FoV (−24◦ to +42◦ × ±22.5◦ around the expected solar wind arrival direction), which nevertheless is capable of measuring the full 3D VDF of the protons and alpha particles arriving at the instrument in the energy range from 200 eV/q to 20 keV/e. Finally, SWA-HIS measures the composition and 3D VDFs of heavy ions in the bulk solar wind as well as those of the major constituents in the suprathermal energy range and those of pick-up ions. The sensor resolves the full 3D VDFs of the prominent heavy ions at a resolution of 5 min in normal mode and 30 s in burst mode. Additionally, SWA-HIS measures 3D VDFs of alpha particles at a 4 s resolution in burst mode. Measurements are over a FoV of −33◦ to +66◦ × ±20◦ around the expected solar wind arrival direction and at energies up to 80 keV/e. The mass resolution (m/∆m) is >5. This paper describes how the three SWA scientific sensors, as delivered to the spacecraft, meet or exceed the performance requirements originally set out to achieve the mission’s science goals. We describe the motivation and specific requirements for each of the three sensors within the SWA suite, their expected science results, their main characteristics, and their operation through the central SWA-DPU. We describe the combined data products that we expect to return from the suite and provide to the Solar Orbiter Archive for use in scientific analyses by members of the wider solar and heliospheric communities. These unique data products will help reveal the nature of the solar wind as a function of both heliocentric distance and solar latitude. Indeed, SWA-HIS measurements of solar wind composition will be the first such measurements made in the inner heliosphere. The SWA data are crucial to efforts to link the in situ measurements of the solar wind made at the spacecraft with remote observations of candidate source regions. This is a novel aspect of the mission which will lead to significant advances in our understanding of the mechanisms accelerating and heating the solar wind, driving eruptions and other transient phenomena on the Sun, and controlling the injection, acceleration, and transport of the energetic particles in the heliosphere.