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The low-electron flux variability (increase/decrease) in the Earth’s radiation belts could cause low-energy Electron Precipitation (EP) to the atmosphere over auroral and South American Magnetic Anomaly (SAMA) regions. This EP into the atmosphere can cause an extra upper atmosphere’s ionization, forming the auroral-type sporadic E layers (Esa) over these regions. The dynamic mechanisms responsible for developing this Esa layer over the auroral region have been established in the literature since the 1960s. In contrast, there are several open questions over the SAMA region, principally due to the absence (or contamination) of the inner radiation belt and EP parameter measurements over this region. Generally, the Esa layer is detected under the influence of geomagnetic storms during the recovery phase, associated with solar wind structures, in which the time duration over the auroral region is considerably greater than the time duration over the SAMA region. The inner radiation belt’s dynamic is investigated during a High-speed Solar wind Stream (September 24-25, 2017), and the hiss wave-particle interactions are the main dynamic mechanism able to trigger the Esa layer’s generation outside the auroral oval. This result is compared with the dynamic mechanisms that can cause particle precipitation in the auroral region, showing that each region presents different physical mechanisms. Additionally, the difference between the time duration of the hiss wave activities and the Esa layers is discussed, highlighting other ingredients mandatory to generate the Esa layer in the SAMA region.

Switchbacks (SBs) are localized structures in the solar wind containing deflections of the magnetic field direction relative to the background solar wind magnetic field. The amplitudes of the magnetic field deflection angles ( θ ) for different SBs vary from ∼40° to ∼160°–170°. Alignment of the perturbations of the magnetic field (Δ B ) and the bulk solar wind velocity (Δ V ) is observed inside SBs so that Δ V ∼ Δ B when the background magnetic field is directed toward the Sun (if the background solar wind magnetic field direction is anti-sunward then Δ V ∼ − Δ B , supporting anti-sunward propagation in the background solar wind frame). This causes spiky enhancements of the radial bulk velocity inside SBs. We have investigated the deviations of SB perturbations from Alfvénicity by evaluating the distribution of the parameter α , defined as the ratio of the parallel to Δ B component of Δ V to Δ V _A = Δ B /4 π n _i m _i inside SBs, i.e., α = V _∣∣ /∣Δ V _A ∣ ( α = ∣Δ V ∣/∣Δ V _A ∣ when Δ V ∼ Δ B ), which quantifies the deviation of the perturbation from an Alfvénic one. Based on Parker Solar Probe (PSP) observations, we show that α inside SBs has systematically lower values than it has in the pristine solar wind: α inside SBs observed during PSP Encounter 1 were distributed in a range from ∼0.2 to ∼0.9. The upper limit on α is constrained by the requirement that the jump in velocity across the switchback boundary be less than the local Alfvén speed. This prevents the onset of shear flow instabilities. The consequence of this limitation is that the perturbation of the proton bulk velocity in SBs with θ > π /3 cannot reach α = 1 (the Alfvénicity condition) and the highest possible α for an SB with θ = π is 0.5. These results have consequences for the interpretation of switchbacks as large amplitude Alfvén waves.

We present the first results study of the effects of the powerful gamma-ray burst GRB 221009A that occurred on 2022 October 9, and was serendipitously recorded by electron and proton detectors on board the four spacecraft of the NASA THEMIS mission. Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars, and, among them, GRB 221009A is so far the brightest burst ever observed due to its enormous energy ( E _γ _ iso ≈ 10 ^55 erg) and proximity (the redshift is z ≈ 0.1505). The THEMIS mission launched in 2008 was designed to study the plasma processes in the Earth’s magnetosphere and the solar wind. The particle flux measurements from the two inner magnetosphere THEMIS probes, THA and THE, and two outer probes (renamed ARTEMIS after 2010), THB and THC, orbiting the Moon captured the dynamics of GRB 221009A with a high time resolution of 4 (up to 8) measurements per second. This allowed us to resolve the fine structure of the GRB and determine the temporal scales of the two main bursts’ spiky structure, complementing the results from gamma-ray space telescopes and detectors.

The dynamics of the electron population in the Earth’s radiation belts affect the upper atmosphere’s ionization level through the low-energy Electron Precipitation (EP). The impact of low-energy EP on the high-latitude ionosphere has been well explained since the 1960’s decade. Conversely, it is still not well understood for the region of the South American Magnetic Anomaly (SAMA). In this study, we present the results of analysis of the strong geomagnetic storm associated with the Interplanetary Coronal Mass Ejection (May 27-28, 2017). The atypical auroral sporadic E layers (Esa) over SAMA are observed in concomitance with the hiss and magnetosonic wave activities in the inner radiation belt. The wave-particle interaction effects have been estimated, and the dynamic mechanisms that caused the low-energy EP over SAMA were investigated. We suggested that the enhancement in pitch angle scattering driven by hiss waves result in the low-energy EP (≥10 keV) into the atmosphere over SAMA. The impact of these precipitations on the ionization rate at the altitude range from 100 to 120 km can generate the Esa layer in this peculiar region. In contrast, we suggested that the low-energy EP (≤1 keV) causes the maximum ionization rate close to 150 km altitude, contributing to the Esa layer occurrence in these altitudes.

The evolution of plasma entropy and the process of plasma energy redistribution at the collisionless plasma shock front are evaluated based on the high temporal resolution data from the four Magnetospheric Multiscale spacecraft during the crossing of the terrestrial bow shock. The ion distribution function has been separated into the populations with different characteristic behaviors in the vicinity of the shock: the upstream core population, the reflected ions, the gyrating ions, the ions trapped in the vicinity of the shock, and the downstream core population. The values of ion and electron moments (density, bulk velocity, and temperature) have been determined separately for these populations. It is shown that the solar wind core population bulk velocity slows down mainly in the ramp with the electrostatic potential increase but not in the foot region as it was supposed. The reflected ion population determines the foot region properties, so the proton temperature peak in the foot region is an effect of the relative motion of the different ion populations, rather than an actual increase in the thermal speed of any of the ion population. The ion entropy evaluated showed a significant increase across the shock: the enhancement of the ion entropy occurs in the foot of the shock front and at the ramp, where the reflected ions are emerging in addition to the upstream solar wind ions, the anisotropy growing to generate the bursts of ion-scale electrostatic waves. The entropy of electrons across the shock does not show a significant change: electron heating goes almost adiabatically.

Observations of the young solar wind by the Parker Solar Probe (PSP) mission reveal the existence of intense plasma wave bursts with frequencies between 0.05 and 0.20 f _ce (tens of hertz up to ∼300 Hz) in the spacecraft frame. The wave bursts are often collocated with inhomogeneities in the solar wind magnetic field, such as local dips in magnitude or sudden directional changes. The observed waves are identified as electromagnetic whistler waves that propagate either sunward, anti-sunward, or in counter-propagating configurations during different burst events. Being generated in the solar wind flow, the waves experience significant Doppler downshift and upshift of wave frequency in the spacecraft frame for sunward and anti-sunward waves, respectively. Their peak amplitudes can be larger than 2 nT, where such values represent up to 10% of the background magnetic field during the interval of study. The amplitude is maximum for propagation parallel to the background magnetic field. We (i) evaluate the properties of these waves by reconstructing their parameters in the plasma frame, (ii) estimate the effective length of the PSP electric field antennas at whistler frequencies, and (iii) discuss the generation mechanism of these waves.

In this paper we investigate the electron pitch-angle diffusion coefficients in the night-side inner magnetosphere around the geostationary orbit (L ~ 7) due to magnetic field deformation. We compare the effects of resonant wave–particle scattering by lower band chorus waves and the adiabaticity violation of electron motion due to the strong curvature of field lines in the vicinity of the equator. For a realistic magnetic field configuration, the nonadiabatic effects are more important than the wave–particle interactions for high energy (> 1 MeV) electrons. For smaller energy, the scattering by waves is more effective than nonadiabatic one. Moreover, the role of nonadiabatic effects increases with particle energy. Therefore, to model electron scattering and transport in the night-side inner magnetosphere, it is important to take into account the peculiarities of high-energy electron dynamics.

The lifetimes of electrons trapped in Earth's radiation belts can be calculated from quasi-linear pitch-angle diffusion by whistler-mode waves, provided that their frequency spectrum is broad enough and/or their average amplitude is not too large. Extensive comparisons between improved analytical lifetime estimates and full numerical calculations have been performed in a broad parameter range representative of a large part of the magnetosphere from L ~ 2 to 6. The effects of observed very oblique whistler waves are taken into account in both numerical and analytical calculations. Analytical lifetimes (and pitch-angle diffusion coefficients) are found to be in good agreement with full numerical calculations based on CRRES and Cluster hiss and lightning-generated wave measurements inside the plasmasphere and Cluster lower-band chorus waves measurements in the outer belt for electron energies ranging from 100 keV to 5 MeV. Comparisons with lifetimes recently obtained from electron flux measurements on SAMPEX, SCATHA, SAC-C and DEMETER also show reasonable agreement.

Nature Communications 6: Article number: 7143 (2015); Published: 15 May 2015; Updated: 26 March 2018 The original HTML version of this Article had an incorrect article number of 8143; it should have been 7143. This has now been corrected in the HTML; the PDF version of the Article was correct from the time of publication.

The quasi-stationary asymmetry of total ozone over Antarctica during spring is studied by TOMS data during the period 1979–2005. Statistics on the amplitude and longitudinal position of zonal anomalies are obtained from the distribution of total ozone along seven individual latitudes at 5-degree intervals between 50° S and 80° S. As shown by the September-November means, the mid-latitude collar of ozone-rich stratospheric air has a sub-Antarctic maximum with a mean location in the quadrant 90° E–180° E and a total ozone level of about 380 DU between 50° S and 60° S. The steady displacement and elongation of the ozone hole under the influence of planetary waves causes a zonal anomaly of low ozone in the sector 0°–60° W with total ozone levels of about 200 DU between 70° S and 80° S. Climatologically, the highest amplitude of the zonal anomaly is 57.2±13.5 DU (relative asymmetry of 32% between high and low ozone levels) at 65° S latitude. A significant eastward shift of approximately 45° in longitude is observed in the total ozone minimum over the Weddell Sea – South Atlantic sector during 1979–2005, whereas the zonal maximum is relatively stable in location. Also apparent is a long-term shift in tropopause temperature distribution in the region. The geographical distribution of the zonal extremes in total ozone for the seven latitudes shows that (i) the extremes exhibit sensitivity to the shape of the Antarctic continent, (ii) the stationarity of the extremes increases poleward above the edge of continent and (iii) the positions of the extremes at the higher latitudes tend to follow the meridionally oriented elements of orography. It is suggested that the radiative influence of Antarctica contributes to the formation of this pattern. Anomalies in the horizontal structure of the tropopause, which appear related to orography, support this view. Mechanisms involved in the formation and decadal change in the total ozone asymmetry, as well as possible influences of the asymmetry on the stratospheric thermal regimes and regional UV irradiance redistribution are discussed.