Radiation exposure at aviation altitudes presents significant health risks to aircrews due to the cumulative effects of ionizing radiation. Physics-based models estimate radiation levels based on geophysical and atmospheric parameters, but often struggle to capture the highly dynamic and complex nature of the radiation environment, limiting their real-time predictive capabilities. To address this challenge, we investigate machine learning (ML) methods to enhance real-time radiation nowcasting. Leveraging newly compiled ML-ready datasets, publicly available at https://dmlab.cs.gsu.edu/rdp/, we train supervised models capable of capturing both linear and non-linear relationships between Geospace conditions and atmospheric radiation levels. Our experiments demonstrate that the XGBoost model achieves approximately 10 percent improvement in prediction accuracy over the considered physics-based model. Furthermore, feature importance analysis reveals that certain Geospace properties, specifically solar polar fields, solar wind properties, and neutron monitor data, are impacting the nowcast of the radiation levels at flight altitudes. These findings suggest meaningful physical relationships between the near-Earth space environment and atmospheric radiation, and highlight the potential of ML-based approaches for operational space weather applications.
Dario Javier Zamora, Facundo Abaca, Bruno Zossi
et al.
The solar wind is a medium characterized by strong turbulence and significant field fluctuations on various scales. Recent observations have revealed that magnetic turbulence exhibits a self-similar behavior. Similarly, high-resolution measurements of the proton density have shown comparable characteristics, prompting several studies into the multifractal properties of these density fluctuations. In this work, we show that low-resolution observations of the solar wind proton density over time, recorded by various spacecraft at Lagrange point L1, also exhibit non-linear and multifractal structures. The novelty of our study lies in the fact that this is the first systematic analysis of solar wind proton density using low-resolution (hourly) data collected by multiple spacecraft at the L1 Lagrange point over a span of 17 years. Furthermore, we interpret our results within the framework of non-extensive statistical mechanics, which appears to be consistent with the observed nonlinear behavior. Based on the data, we successfully validate the q-triplet predicted by non-extensive statistical theory. To the best of our knowledge, this represents the most rigorous and systematic validation to date of the q-triplet in the solar wind.
AbstractMicrobursts are short duration intensifications in precipitating electron flux that are believed to be a significant contributor to electron losses in the magnetosphere. Microbursts have been observed in the form of bouncing electron packets, which offer a unique opportunity to study their properties and importance as a loss process. We present a collection of bouncing microbursts observed by the HILT instrument on SAMPEX from 1994 to 2004. We analyze the locations of the bouncing microbursts in L and MLT and find they align well with the properties of relativistic microbursts as a whole. We find that the majority of bouncing microbursts observed by SAMPEX have scale sizes of ∼30 km at the point of observation, or ∼300 km when mapped to the magnetic equator. The time separation between the peaks of these bouncing microbursts is usually either half a bounce period or a whole bounce period.
C. H. Zepeda-Fernández, F. A. Sánchez-Arévalo, E. Moreno-Barbosa
The solar radiation are electromagnetic waves, composed of infrared, visible spectrum and ultraviolet. The infrared component is the cause of thermal energy, the visible spectrum allows to see and the ultraviolet component is the most energetic part and dangerous for the human body (skin and eyes). The ultraviolet rays are divided in a wavelength range, in three parts; called UVA (100-280 nm), UVB (280-315 nm) and UVC (315-400 nm). The UVC are the most energetic (followed by the UVB rays ), however are stopped in the ozone layer. In this work it shown a statistical analysis of the UVB index measured by five station in Mexico City, from the years 2000 to 2022. Through a Gaussian fit distribution, it was found that the range when the IUVB value exceeds the value of seven, which is from 11:00 to 16:00, having an average mean value of 13:09 hrs. $\pm$ 4 min. i.e. the time at which the UVB index reaches its maximum value. This occurs in the months from February to October. More than 80% of radiation is for UVB values less than 7 and less than the remaining 20% is for IUVB values greater than 7. Finally, it was possible to observe that the mean value per year, reaches its maximum when the solar cycles occurs, which was in the years 2003 and 2013.
AbstractLower‐band chorus waves are known to play dual roles in radiation belt dynamics (electron acceleration and precipitation), and understanding their properties and excitation is very important. A systematic study of chorus waves properties in terms of background plasma parameters (electron perpendicular beta β⊥ and the ratio of plasma frequency to electron cyclotron frequency fpe/fce) has not been performed previously. We use burst‐mode data from Van Allen Probe A from 2012 to 2019 and develop an algorithm to extract individual lower band rising tone chorus elements. We statistically analyze four properties of rising tone chorus elements: time duration τ, frequency width Δf, chirping rate Γ, and maximum amplitude Ia. Statistical results show typical properties of chorus waves: Ia ∼ 0.09 nT, Δf ∼ 0.08fce, Γ ∼ 2 × 103 Hz/s, τ ∼ 0.015–0.25 s. On the nightside and dawnside, Γ shows wider spread and is more distributed over larger values, which is associated with the wider distribution of β⊥. Chorus waves at duskside and dayside have larger values of τ, associated with smaller β⊥ and larger fpe/fce. The dependence of chorus wave properties on background plasma parameters is also examined. We show that normalized Δf has positive correlation with β⊥ and fpe/fce. Normalized τ shows negative correlation with β⊥ and positive correlation with fpe/fce. Normalized Γ and Ia show positive correlations with β⊥ and negative correlations with fpe/fce. These results help us better understand chorus waves excitation and their relation to the microburst.
Solar wind turbulence is often perceived as weakly compressible and the density fluctuations remain poorly understood both theoretically and observationally. Compressible magnetohydrodynamic simulations provide useful insights into the nature of density fluctuations. We discuss a few important effects related to 3D simulations of turbulence and in-situ observations. The observed quantities such as the power spectrum and variance depend on the angle between the sampling trajectory and the mean magnetic field due to anisotropy of the turbulence. The anisotropy effect is stronger at smaller scales and lower plasma beta. Additionally, in-situ measurements tend to exhibit a broad range of variations, even though they could be drawn from the same population with the defined averages, so a careful averaging may be needed to reveal the scaling relations between density variations and other turbulence quantities such as turbulent Mach number from observations.
Negative ions have been detected in abundance in recent years by spacecraft across the solar system. These detections were, however, made by instruments not designed for this purpose and, as such, significant uncertainties remain regarding the prevalence of these unexpected plasma components. In this article, the phenomenon of photodetachment is examined and experimentally and theoretically derived cross-sections are used to calculate photodetachment rates for a range of atomic and molecular negative ions subjected to the solar photon spectrum. These rates are applied to negative ions outflowing from Europa, Enceladus, Titan, Dione and Rhea and their trajectories are traced to constrain source production rates and the extent to which negative ions are able to pervade the surrounding space environments. Predictions are also made for further negative ion populations in the outer solar system with Triton used as an illustrative example. This study demonstrates how, at increased heliocentric distances, negative ions can form stable ambient plasma populations and can be exploited by future missions to the outer solar system.
AbstractTotal electron count (TEC) enhancements due to space weather are a threat to communications and global positioning systems. It is known that TEC enhancements occur during magnetic storms and can cover large areas for many hours, but it is also not uncommon for TEC enhancements on the order of a few TEC units to occur during substorms. Although much is known about storm‐associated TECs, the temporal and spatial characteristics of substorm‐associated TECs are not well established. By combining two‐dimensional maps of TECs over North America and Greenland and with maps of ionospheric currents derived with the spherical elementary current method [Weygand et al., 2011], we investigate the temporal and spatial changes of TEC enhancement events for both a single substorm and for multiple substorms combined using a two‐dimensional superposed‐epoch analysis. Both the single event analysis and the statistical analysis show an increase of TECs during the expansion phase. Substorm values of the TEC enhancements peak within 10 min after auroral onset and recover to nominal levels after about 40 min. TEC enhancements occur mainly within the nightside region 1 current system and cover millions of square kilometers. Furthermore, these enhancements appear to be associated with enhanced precipitating electron fluxes. These results address one of goals of the Space Weather Action Plan, which are to establish benchmarks for space weather events and improve modeling and prediction of their impacts on infrastructure.
Based on Magnetospheric Multiscale (MMS) observations from the Earth's bow shock, we have identified two plasma heating processes that operate at quasi-perpendicular shocks. Ions are subject to stochastic heating in a process controlled by the heating function $χ_j = m_j q_j^{-1} B^{-2}\mathrm{div}(\mathbf{E}_\perp)$ for particles with mass $m_j$ and charge $q_j$ in the electric and magnetic fields $\mathbf{E}$ and $\mathbf{B}$. Test particle simulations are employed to identify the parameter ranges for bulk heating and stochastic acceleration of particles in the tail of the distribution function. The simulation results are used to show that ion heating and acceleration in the studied bow shock crossings is accomplished by waves at frequencies (1-10)$f_{cp}$ (proton gyrofrequency) for the bulk heating, and $f>10f_{cp}$ for the tail acceleration. When electrons are not in the stochastic heating regime, $|χ_e|<1$, they undergo a quasi-adiabatic heating process characterized by the isotropic temperature relation $T/B=(T_0/B_0)(B_0/B)^{1/3}$. This is obtained when the energy gain from the conservation of the magnetic moment is redistributed to the parallel energy component through the scattering by waves. The results reported in this paper may also be applicable to particle heating and acceleration at astrophysical shocks.
Deepthi Ayyagari, Sumanjit Chakraborty, Saurabh Das
et al.
This paper emphasizes on NavIC's performance in ionospheric studies over the Indian subcontinent region. The study is performed using data of one year (2017-18) at IIT Indore, a location near the northern crest of Equatorial Ionization Anomaly (EIA). It has been observed that even without the individual error corrections, the results are within $\pm20\%$ of NavIC VTEC estimates observed over the 1\ensuremath{^{\circ}} x 1\ensuremath{^{\circ}} grid of IPP surrounding the GPS VTEC estimates for most of the time. Additionally, ionospheric response during two distinct geomagnetic storms (September 08 and 28, 2017) at the same location and other IGS stations covering the Indian subcontinent using both GPS and NavIC has also been presented. This analysis revealed similar variations in TEC during the geomagnetic storms of September 2017, indicating the suitability of NavIC to study space weather events along with the ionospheric studies over the Indian subcontinent.
Abstract Being one of the first generation of space scientists who entered this field right after the space became accessible to in situ observations, I had good luck of addressing some of the basic questions in this field from the early years of my carrier. These are development of global convection in the magnetosphere when the interplanetary magnetic field has the southward polarity, changes in the structure of the magnetotail leading to the onset of substorm expansion phase, and physics of the plasmapause formation. My career culminated with promotion and implementation of the Geotail spacecraft mission. In this article I shall present my personal recollections on these efforts including interactions with colleagues worldwide who shared the common interest.
Francesco Pecora, Antonella Greco, Qiang Hu
et al.
A novel technique is presented for describing and visualizing the local topology of the magnetic field using single-spacecraft data in the solar wind. The approach merges two established techniques: the Grad-Shafranov (GS) reconstruction method, which provides a plausible regional two-dimensional magnetic field surrounding the spacecraft trajectory, and the Partial Variance of Increments (PVI) technique that identifies coherent magnetic structures, such as current sheets. When applied to one month of Wind magnetic field data at 1-minute resolution, we find that the quasi-two-dimensional turbulence emerges as a sea of magnetic islands and current sheets. Statistical analysis confirms that current sheets associated with high values of PVI are mostly located between and within the GS magnetic islands, corresponding to X-points and internal boundaries. The method shows great promise for visualizing and analyzing single-spacecraft data from missions such as Parker Solar Probe and Solar Orbiter, as well as 1 AU Space Weather monitors such as ACE, Wind and IMAP.
Although the origins of slow solar wind are unclear, there is increasing evidence that at least some of it is released in a steady state on over-expanded coronal hole magnetic field lines. This type of slow wind has similar properties to the fast solar wind, including a high degree of Alfvénicity. In this study a combination of proton, alpha particle, and electron measurements are used to investigate the kinetic properties of a single interval of slow Alfvénic wind at 0.35 AU. It is shown that this slow Alfvénic interval is characterised by high alpha particle abundances, pronounced alpha-proton differential streaming, strong proton beams, and large alpha to proton temperature ratios. These are all features observed consistently in the fast solar wind, adding evidence that at least some Alfvénic slow solar wind also originates in coronal holes. Observed differences between speed, mass flux, and electron temperature between slow Alfvénic and fast winds are explained by differing magnetic field geometry in the lower corona.
An X1.7 flare at 10:15 UT and a halo CME with a projected speed of 942 km/s erupted from NOAA solar active region 9393 located at N20W19, were observed on 2001 March 29. When the CME reached the Earth, it triggered a super geomagnetic storm (hereafter super storm). We find that the CME always moved towards the Earth according to the intensity-time profiles of protons with different energies. The solar wind parameters responsible for the main phase of the super storm occurred on March 31, 2001 is analyzed taking into account the delayed geomagnetic effect of solar wind at the L1 point and using the SYM-H index. According to the variation properties of SYM-H index during the main phase of the super storm, the main phase of the super storm is divided into two parts. A comparative study of solar wind parameters responsible for the two parts shows the evidence that the solar wind density plays a significant role in transferring solar wind energy into the magnetosphere, besides the southward magnetic field and solar wind speed.
AbstractThe magnetometer data for the Cassini mission (2004–2016) are used to derive a model of Saturn's meridional magnetic field lines. Using a bin map of the Bρ and Bz field components, the field lines can be traced from the equator to high latitudes in the inner magnetosphere. The traces reveal a magnetic field greatly compressed on the dayside and highly elongated on the nightside, which are presumably the effects of solar wind compression and viscous flow around the magnetosphere. A model of the traced field lines can accommodate this day‐night asymmetry and offer a way to connect various places in the magnetosphere. This model can be adjusted for magnetodisk warping by using solar latitude. The field line traces can be mapped down to the ionosphere using an offset dipole. The dayside magnetopause (L = 21) is mapped to colatitudes of ~13° in the north and ~16° in the south, while for L > 25 on the nightside, the mapped field lines approach asymptotic limits of ~16° in the north and ~18° in the south.
A methodology is presented for the differential drag control of a large fleet of propulsion-less satellites deployed in the same orbit. The controller places satellites into a constellation with specified angular offsets and zero-relative speed. Time optimal phasing is achieved by first determining an appropriate relative placement, i.e. the order of the satellites. A second optimization problem is then solved as a large coupled system to find the drag command profile required for each satellite. The control authority is the available ratio of low-drag to high-drag ballistic coefficients of the satellites when operating in their background mode. The controller is able to successfully phase constellations with up to 100 satellites in simulations. On-orbit performance of the controller is demonstrated by phasing the Planet Flock 2p constellation of twelve cubesats launched in June 2016 into a 510 km sun-synchronous orbit.