We present a novel framework for analyzing magnetic topology by combining the field-line slippage rate with persistent homology. The slippage rate provides a local, physically motivated scalar field sensitive to gradients in field-line connectivity, while persistent homology enables the automated extraction of dominant topological features. This approach is particularly efficient for the analysis of large datasets of complex magnetic field configurations. Applied to magnetospheric configurations from two empirical models, the method identifies distinct magnetotail regimes associated with magnetic cusps, X-lines and flux ropes. We show that the location of strong near-Earth slippage rate regions, in both models, is primarily governed by magnetic pressure balance, demonstrating that this combined methodology provides a robust, scalable framework for diagnosing and systematically characterizing complex magnetic structures in large datasets.

Fully depleted CMOS sensors represent a significant step forward in radiation detection, combining the advantages of monolithic active pixel sensors with the enhanced signal collection efficiency of depleted bulk materials. The ARCADIA Collaboration established a technology platform for the development and production of deep sub-micron fully depleted CMOS monolithic sensors with excellent collection efficiency, advancing this semiconductor detector technology with IP cores, ASICs, and back-end dedicated acquisition systems. The sensor technology was demonstrated on system-ready full chip monolithic active pixel sensors with high rate capability and very low power for the detection of charged particles and photons. Innovative CMOS monolithic LGADs featuring a shallow gain layer and implementing a low-gain avalanche diode were developed for time-of-flight detectors, while other prototype ASICs have implemented multi-threshold photon-counting architectures for X-ray imaging. The implementation of fully depleted monolithic strip sensors with embedded electronics and low power density makes the proposed approach a good candidate for future detectors in space applications. The ARCADIA technology will find applications in medical instruments, nuclear imaging and dosimetry, frontier detectors for experimental high energy, and astroparticle physics. This review details the main development achievements by describing the technology demonstrators fabricated and tested and provides a detailed overview of the characteristics and architecture of the ARCADIA-MD3 full-chip monolithic active pixel sensor.

The CSES-01 satellite, with its versatile set of payloads, is able to detect short bursts of lightning-induced electron precipitation (LEP) simultaneously with injected up-going whistler waves. The electron bursts are identified individually for each telescope of the low-energy detector of the high-energy particle package (HEPP-L) within the energy range from 100 to 250 keV. The whistler wave detection is based on the power spectral density of the magnetic field in the frequency range from 1 to 10 kHz, measured by the search coil magnetometer (SCM). The wave and particle observations of CSES-01 are complemented by the ground-based lightning network of the World Wide Lightning Location Network (WWLLN). The found LEP events occur within ≤120 ms of the causative lightning discharge. A statistical study of the LEP events has been performed, which includes a background estimation for the wave-particle correlation. The identified LEP events are found to be shifted significantly polewards of the initial lightning and extend over some 1000 km longitudinally. In addition, it was found that the distance from the LEP event to the lightning decreases as the absolute lightning latitude increases. This finding is in agreement with models of electron interaction with obliquely propagating lightning-generated whistlers and observations from previous missions.

We introduce the Whistler Identification by Spectral Power Estimation and Recognition (WhISPER) algorithm, a novel automated technique for detecting whistler waves in the top side of the Earth’s ionosphere. WhISPER is the first step towards a comprehensive system designed to accumulate and analyze a large dataset of whistler observations, which has been developed to advance our understanding of whistler generation and propagation. Unlike conventional image-correlation-based techniques, WhISPER identifies whistlers based on their energy content, enhancing computational efficiency. This work presents the results of applying WhISPER to four years (2019–2022) of top-side ionospheric magnetic field data. A statistical analysis of over 800,000 detected whistlers reveals a strong correlation with lightning activity and (as expected) higher occurrence rates during local summer months. The presented results demonstrate the excellent performance of the WhISPER technique in identifying whistler events.

The intricate behavior of particle acceleration and transport mechanisms complicates the overall efforts in formulating a comprehensive understanding of solar energetic particle (SEP) events; these efforts include observations of low-energy particles (from tens of keV to hundreds of MeV) by space-borne instruments and measurements by the ground-based neutron monitors of the secondary particles generated in the Earth atmosphere by SEPs in the GeV range. Numerous space-borne missions provided good data on the nature/characteristics of these solar particles in past solar cycles, but more recently-concurrently with the rise toward the maximum of solar cycle 25-the High-Energy Particle Detector (HEPD-01) proved to be well suited for the study of solar physics and space weather. Its nominal 30-300 MeV energy range for protons can enlarge the detection capabilities of solar particles at low Earth orbit, closer to the injection limit of many SEP events. In this work, we characterize three SEP events within the first six months of 2022 through spectral and velocity dispersion analysis, assessing the response of HEPD-01 to >M1 events.

Cosmic rays' interactions with the residual atmosphere surrounding the Earth produce a variety of particles, like electrons, positrons, protons, anti-protons, and Helium nuclei that can be observed below the local geomagnetic cutoff. In this work, we present new measurements of downward-going, albedo proton fluxes with kinetic energy in the range ∼40–∼250 MeV, performed by the High-Energy Particle Detector (HEPD-01) on board of the China Seismo-Electromagnetic Satellite - CSES-01 - at an altitude of ∼500 km. Employing a dedicated trajectory-tracing simulation routine, the protons collected by HEPD-01 are classified into quasi-trapped (QT), long lifetime (≳10 s) particles concentrating in the equatorial region of the Earth, and un-trapped (UT), distributed at all latitudes; the latter includes both precipitating short lifetime particles (UTS) and pseudo-trapped long lifetime (UTL) populations, abundant in the so-called penumbra regions. The temporal trend of re-entrant protons between 2018 and 2022 is also reported, assessing the stability of such population during the data-taking period of HEPD-01; this highlights their independence from the long-term modulating effect of the solar activity.

In this paper we report the detection of five strong gamma-ray bursts (GRBs) by the High-Energy Particle Detector (HEPD-01) mounted on board the China Seismo-Electromagnetic Satellite, operational since 2018 on a Sun-synchronous polar orbit at a ∼507 km altitude and 97° inclination. HEPD-01 was designed to detect high-energy electrons in the energy range 3–100 MeV, protons in the range 30–300 MeV, and light nuclei in the range 30–300 MeV n −1 . Nonetheless, Monte Carlo simulations have shown HEPD-01 is sensitive to gamma-ray photons in the energy range 300 keV–50 MeV, even if with a moderate effective area above ∼5 MeV. A dedicated time correlation analysis between GRBs reported in literature and signals from a set of HEPD-01 trigger configuration masks has confirmed the anticipated detector sensitivity to high-energy photons. A comparison between the simultaneous time profiles of HEPD-01 electron fluxes and photons from GRB190114C, GRB190305A, GRB190928A, GRB200826B, and GRB211211A has shown a remarkable similarity, in spite of the different energy ranges. The high-energy response, with peak sensitivity at about 2 MeV, and moderate effective area of the detector in the actual flight configuration explain why these five GRBs, characterized by a fluence above ∼3 × 10 −5 erg cm −2 in the energy interval 300 keV–50 MeV, have been detected.

The ARCADIA (Advanced Readout CMOS Architectures with Depleted Integrated sensor Arrays) collaboration has developed $25 \mu m$ pitch Fully Depleted Monolithic Active Pixel Sensors (MAPS) based on a modified 110 nm CMOS process in collaboration with LFoundry. This work illustrates a set of simulations performed on this detector technology, with the aim of investigating its capabilities for radiation detection applications. Three-dimensional Technology Computer Aided Design (TCAD) simulations have been performed in order to extract the electric field and electrostatic potential maps suitable to execute Monte Carlo simulations, providing high statistics of particle-sensor interaction in a reasonable computing time. The simulation flow will be described in detail and the main results will be pointed out.

Ground-based very low frequency (VLF; 10-30kHz) transmitters have been found in previous studies to emit whistler waves that can re- sonate with high-energy particles (>100keV) in the radiation belt, causing energetic electron precipitation via pitch angle scattering. In the attempt to find a similar mechanism responsible for electron precipitation due to EM waves emitted during seismic events, we ha- ve analysed three years of data (2019-2021) from the China Seismo- Electromagnetic Satellite (CSES) and the NOAA POES satellites. We found enhanced electron fluxes due to the 19.8kHz waves of the NWC transmitter in Australia at L-shell values of about 1.5 and 1.8 at energies up to 400keV in the data of the CSES and NOAA POES-19 sa- tellite, respectively. The enhanced fluxes can be followed along the drift shells from Australia eastwards, and are observed to be lost in the the South Atlantic Anomaly (SAA) due to the interaction with the atmosphere. The high energy resolution of the HEPP-L detector on board CSES of 11keV from 0.1 to 3MeV allows a detailed study of the signal and we will present the expected energy-dispersed wisp struc- ture in L-shell. Finally, we will present our latest results on the identification of isolated electron bursts and the assignment to dif- ferent VLF transmitters, which includes the correlation of VLF wave measurements from ground and space-based instruments to determined on/off periods of the transmitters.

This paper presents the project Comprehensive spAce wEather Studies for the ASPIS prototype Realization (CAESAR), which aims to tackle the relevant aspects of Space Weather (SWE) science and develop a prototype of the scientific data centre for Space Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather InfraStructure). To this end, CAESAR involves the majority of the SWE Italian community, bringing together 10 Italian institutions as partners, and a total of 92 researchers. The CAESAR approach encompasses the whole chain of phenomena from the Sun to Earth up to planetary environments in a multidisciplinary, comprehensive, and unprecedented way. Detailed and integrated studies are being performed on a number of well-observed “target SWE events”, which exhibit noticeable SWE characteristics from several SWE perspectives. CAESAR investigations synergistically exploit a great variety of different products (datasets, codes, models), both long-standing and novel, that will be made available in the ASPIS prototype: this will consist of a relational database (DB), an interface, and a wiki-like documentation structure. The DB will be accessed through both a Web graphical interface and the ASPIS.py module, i.e., a library of functions in Python, which will be available for download and installation. The ASPIS prototype will unify multiple SWE resources through a flexible and adaptable architecture, and will integrate currently available international SWE assets to foster scientific studies and advance forecasting capabilities.

High-energy, long gamma-ray bursts (GRBs) can be generated by the core collapse of massive stars at the end of their lives. When they happen in the close-by universe they can be exceptionally bright, as seen from the Earth in the case of the recent, giant, long-lasting GRB221009A. GRB221009A was produced by a collapsing star with a redshift of 0.152: this event was observed by many gamma-ray space experiments, which also detected an extraordinary long gamma-ray afterglow. The exceptionally large fluence of the prompt emission of about 0.013 erg cm −2 illuminated a large geographical region centered on India and including Europe and Asia. We report in this paper the observation of sudden electron flux changes correlated with GRB221009A and measured by the HEPP-L charged particle detector on board the China Seismo-Electromagnetic Satellite, which was orbiting over Europe at the time of the GRB event. The time structure of the observed electron flux closely matches the very distinctive time dependence of the photon flux associated with the main part of the emission at around 13:20 UTC on 2022 October 9. To test the origin of these signals, we set up a simplified simulation of one HEPP-L subdetector: the results of this analysis suggest that the signals observed are mostly due to electrons created within the aluminum collimator surrounding the silicon detector, providing real-time monitoring of the very intense photon fluxes. We discuss the implications of this observation for existing and forthcoming particle detectors on low Earth orbits.

This work reports on the design of CMOS-integrated sensors for radiation detection, incorporating an avalanche multiplication layer to amplify the signal generated by the incidence of a charged particle. The avalanche gain, obtained with a dedicated implantation, is used to enhance the Signal-to-Noise Ratio of the sensor signal, and thus to increase its charge and timing resolution. The proposed devices are obtained with the modification of a 110nm CMOS process customized for the production of Fully Depleted Monolithic Active Pixel Sensors, and are suitable for the fabrication of pixelated large-area Time-Of-Flight detectors.

Earth’s atmosphere, whose ionization stability plays a fundamental role for the evolution and endurance of life, is exposed to the effect of cosmic explosions producing high energy Gamma-ray-bursts. Being able to abruptly increase the atmospheric ionization, they might deplete stratospheric ozone on a global scale. During the last decades, an average of more than one Gamma-ray-burst per day were recorded. Nevertheless, measurable effects on the ionosphere were rarely observed, in any case on its bottom-side (from about 60 km up to about 350 km of altitude). Here, we report evidence of an intense top-side (about 500 km) ionospheric perturbation induced by significant sudden ionospheric disturbance, and a large variation of the ionospheric electric field at 500 km, which are both correlated with the October 9, 2022 Gamma-ray-burst (GRB221009A). Gamma-ray bursts (GRBs) are known to have impact on Earth’s lower ionosphere, but GRB impacts on the upper ionosphere was not observed before. Here, the authors show strong electric field variation at 500 km in the ionosphere caused by GRB221009A.

Earthquake monitoring plays a key role in human life protection, especially in highly populated areas of the Earth. First indications have been found in SAMPEX and NOAA satellite data that particle fluxes of trapped electrons in the Van Allen belts can be correlated to seismic activity on the ground. Within the framework of the CSES mission, a systematic analysis of the electron flux, within the invariant phase space in the L-shell and equatorial pitch angle, has started with the goal to identify short-term variations of the flux (particle bursts) in conjunction with seismic activity. This analysis is based on the statistical evaluation of the flux measurements and built to be potentially implemented in an online monitoring system. The first milestone in that direction has been achieved, providing a stable background estimation. With the injection of artificial signals, the efficiency of the method was evaluated and found to be better than 95% for isolated (one per day) and short (∼3 min) signals with a significance ≥ 5σ above the background. The developed method is set up in a manner to be easily applicable to data from different instruments and satellites. This article presents the studied datasets of the low-energy HEPP instrument onboard the CSES-01 satellite and the electron telescopes of the MEPED detector onboard the NOAA POES-19 satellite, introduces the method for the background estimation, and discusses the first correlation studies of particle bursts with geomagnetic indices obtained within this framework.

In this paper we report the detection of five strong Gamma-Ray Bursts (GRBs) by the High-Energy Particle Detector (HEPD-01) mounted on board the China Seismo-Electromagnetic Satellite (CSES-01), operational since 2018 on a Sun-synchronous polar orbit at a $\sim$ 507 km altitude and 97$^\circ$ inclination. HEPD-01 was designed to detect high-energy electrons in the energy range 3 - 100 MeV, protons in the range 30 - 300 MeV, and light nuclei in the range 30 - 300 MeV/n. Nonetheless, Monte Carlo simulations have shown HEPD-01 is sensitive to gamma-ray photons in the energy range 300 keV - 50 MeV, even if with a moderate effective area above $\sim$ 5 MeV. A dedicated time correlation analysis between GRBs reported in literature and signals from a set of HEPD-01 trigger configuration masks has confirmed the anticipated detector sensitivity to high-energy photons. A comparison between the simultaneous time profiles of HEPD-01 electron fluxes and photons from GRB190114C, GRB190305A, GRB190928A, GRB200826B and GRB211211A has shown a remarkable similarity, in spite of the different energy ranges. The high-energy response, with peak sensitivity at about 2 MeV, and moderate effective area of the detector in the actual flight configuration explain why these five GRBs, characterised by a fluence above $\sim$ 3 $\times$ 10$^{-5}$ erg cm$^{-2}$ in the energy interval 300 keV - 50 MeV, have been detected.

The development of novel Monolithic Active Pixel Sensor (MAPS) technologies has been pursued by several collaborations in the last two decades. The ARCADIA project aims to design fully depleted MAPS for medical, space, HEP and X-ray detection applications, that can be produced with a commercial 110 nm CMOS production process. Among the test structures of the first two engineering runs of the project, passive pixel arrays with different pitches and layouts were included. The main characteristics of the produced devices in terms of dark current, depletion voltage, punch through current and pixel capacitance have been evaluated from IV and CV characteristics of the pixel arrays. Groups of four samples have been extracted from as many different positions within each wafer and electrically characterized to obtain information on the variability in the pixel operating voltage range and in the pixel dark current, reflecting variations related to the employed production process. The experimental data demonstrated a good uniformity in the considered parameters for different sample positions within the produced wafers, as well as for samples extracted from different wafers with the same substrate type.

Monolithic Active Pixel Sensors (MAPS) are a promising technology that provides large sensitive areas at potentially low power consumption and low material budget. The ARCADIA project is developing Fully Depleted MAPS (FD-MAPS) with an innovative sensor design, that uses a backside bias to improve charge collection efficiency and timing over a wide range of operational and environmental conditions. The ARCADIA collaboration has produced a large set of prototypes in the first two engineering runs, with the main design consisting of a 512 x 512 pixel matrix with 25 mu m pixel pitch and other smaller active sensor arrays. Test structures of pixel matrices with pixel pitches ranging from 10 to 50 mu m and total thicknesses of 50 to 200 mu m have also been included, to ease the characterization of the sensors independently from integrated electronics. We give an overview of the status of the project and then focus on the characterization of the passive pixel matrices which include Capacitance-Voltage (CV) and Current-Voltage (IV), as well as Transient Current Technique (TCT) measurements with a red and an infrared laser. We could confirm a single pixel capacitance below 5 fF for pixels with 25 mu m pitch, and a 90% charge collection of MIP-like charge depositions within 12 ns in 100 mu m active thickness. These results are complemented and supported by Technology Computer Aided Design (TCAD) simulations.

Time-dependent energy spectra of galactic cosmic rays (GCRs) carry crucial information regarding their origin and propagation throughout the interstellar environment. When observed at the Earth, after traversing the interplanetary medium, such spectra are heavily affected by the solar wind and the embedded solar magnetic field permeating the inner sectors of the heliosphere. The activity of the Sun changes significantly over an 11 yr solar cycle—and so does the effect on cosmic particles; this translates into a phenomenon called solar modulation. Moreover, GCR spectra during different epochs of solar activity provide invaluable information for a complete understanding of the plethora of mechanisms taking place in various layers of the Sun’s atmosphere and how they evolve over time. The High-Energy Particle Detector (HEPD-01) has been continuously collecting data since 2018 August, during the quiet phase between solar cycles 24 and 25; the activity of the Sun is slowly but steadily rising and is expected to peak around 2025/2026. In this paper, we present the first spectra for ∼50–250 MeV galactic protons measured by the HEPD-01 instrument—placed on board the CSES-01 satellite—from 2018 August to 2022 March over a one-Carrington-rotation time basis. Such data are compared to the ones from other spaceborne experiments, present (e.g., EPHIN, Parker Solar Probe) and past (PAMELA), and to a state-of-the-art three-dimensional model describing the GCRs propagation through the heliosphere.

The ARCADIA collaboration is developing fully-depleted (FD) Monolithic Active Pixel Sensors (MAPS) in a 110 nm CMOS process in collaboration with LFoundry. The sensor design incorporates an n+ collection node within a n-type epi-layer on top of a high-resistivity n-type substrate and p+ backside. Thus, the pn-junction sits on the backside and through an applied backside bias, the full substrate gets depleted. The targeted applications of this technology range from future high energy physics experiments to space applications, and medical and industrial scanners. Together, these applications set the minimum requirements on the detector: data collec-tion at hit rates of (10-100) MHz/cm2, full signal processing within (1-10) mu s, maximum power consumption (5-20) mW/cm2 and radiation tolerances of up to 3.4 Mrad or 6.2 x 1012 1 MeV neutron equivalent fluence. In order to proof the performance of the technology, a demonstrator chip of 512 x 512 pixels with 25 mu m pitch was designed and fabricated in a first engineering run in 2021, together with additional test structures of pixel and strip arrays with different pitches and sensor geometries. The production run has produced functional passive and active pixel matrices. Earlier studies have shown that positive oxide charges and traps at the Si-SiO2 interface, introduced by ionising radiation, affect the depletion region around the collection electrode, increasing the pixel capacitance. By varying the gap size between collection node and pwells, the geometry can be optimised to keep the capacitance low also after irradiation. To study the performance after irradiation, of the optimised diode designs, the passive pixel matrices were irradiated with doses up to 10 Mrad (SiO2) using a X-ray tube with a Tungsten anode. The measurements are complemented by TCAD simulations. The maximum capacitance increase after irradiation was found to reach 6 and 12 fF/pixel for pixel pitches of 25 and 50 mu m, respectively. The relative capacitance increase after irradiation has hereby been found to reach up to 250% after a dose of 10 Mrad.