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In this work, we investigate how the complex structure found in solar wind proton velocity distribution functions (VDFs), rather than the commonly assumed two-component bi-Maxwellian structure, affects the onset and evolution of parallel-propagating microinstabilities. We use theArbitrary Linear Plasma Solver, a numerical dispersion solver, to find the real frequencies and growth/damping rates of the Alfvén modes calculated for proton VDFs extracted from Wind spacecraft observations of the solar wind. We compare this wave behavior to that obtained by applying the same procedure to core-and-beam bi-Maxwellian fits of the Wind proton VDFs. We find several significant differences in the plasma waves obtained for the extracted data and bi-Maxwellian fits, including a strong dependence of the growth/damping rate on the shape of the VDF. By applying the quasilinear diffusion operator to these VDFs, we pinpoint resonantly interacting regions in velocity space where differences in VDF structure significantly affect the wave growth and damping rates. This demonstration of the sensitive dependence of Alfvén mode behavior on VDF structure may explain why the Alfvén ion-cyclotron instability thresholds predicted by linear theory for bi-Maxwellian models of solar wind proton background VDFs do not entirely constrain spacecraft observations of solar wind proton VDFs, such as those made by the Wind spacecraft.

 

Streamer-blowout coronal mass ejections (SBO-CMEs) are the dominant CME population during solar minimum. Although they are typically slow and lack clear low-coronal signatures, they can cause geomagnetic storms. With the aid of extrapolated coronal fields and remote observations of the off-limb low corona, we study the initiation of an SBO-CME preceded by consecutive CME eruptions consistent with a multi-stage sympathetic breakout scenario. From inner-heliospheric Parker Solar Probe (PSP) observations, it is evident that the SBO-CME is interacting with the heliospheric magnetic field and plasma sheet structures draped about the CME flux rope. We estimate that 18 ± 11% of the CME’s azimuthal magnetic flux has been eroded through magnetic reconnection and that this erosion began after a heliospheric distance of ∼0.35 AU from the Sun was reached. This observational study has important implications for understanding the initiation of SBO-CMEs and their interaction with the heliospheric surroundings. 

Stealth coronal mass ejections (CMEs) are eruptions from the Sun that are not associated with appreciable low-coronal signatures. Because they often cannot be linked to a well-defined source region on the Sun, analysis of their initial magnetic configuration and eruption dynamics is particularly problematic. In this article, we address this issue by undertaking the first attempt at predicting the magnetic fields of a stealth CME that erupted in 2020 June from the Earth-facing Sun. We estimate its source region with the aid of off-limb observations from a secondary viewpoint and photospheric magnetic field extrapolations. We then employ the Open Solar Physics Rapid Ensemble Information modeling suite to evaluate its early evolution and forward model its magnetic fields up to Parker Solar Probe, which detected the CME in situ at a heliocentric distance of 0.5 au. We compare our hindcast prediction with in situ measurements and a set of flux-rope reconstructions, obtaining encouraging agreement on arrival time, spacecraft-crossing location, and magnetic field profiles. This work represents a first step toward reliable understanding and forecasting of the magnetic configuration of stealth CMEs and slow streamer-blowout events.

 

Abstract The Parker Solar Probe (PSP) routinely observes magnetic field deflections in the solar wind at distances less than 0.3 au from the Sun. These deflections are related to structures commonly called “switchbacks” (SBs), whose origins and characteristic properties are currently debated. Here, we use a database of visually selected SB intervals—and regions of solar wind plasma measured just before and after each SB—to examine plasma parameters, turbulent spectra from inertial to dissipation scales, and intermittency effects in these intervals. We find that many features, such as perpendicular stochastic heating rates and turbulence spectral slopes are fairly similar inside and outside of SBs. However, important kinetic properties, such as the characteristic break scale between the inertial to dissipation ranges differ inside and outside these intervals, as does the level of intermittency, which is notably enhanced inside SBs and in their close proximity, most likely due to magnetic field and velocity shears observed at the edges. We conclude that the plasma inside and outside of an SB, in most of the observed cases, belongs to the same stream, and that the evolution of these structures is most likely regulated by kinetic processes, which dominate small-scale structures at the SB edges. 

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.

 

Abstract This letter exploits the radial alignment between the Parker Solar Probe and BepiColombo in late 2022 February, when both spacecraft were within Mercury’s orbit. This allows the study of the turbulent evolution, namely, the change in spectral and intermittency properties, of the same plasma parcel during its expansion from 0.11 to 0.33 au, a still unexplored region. The observational analysis of the solar wind turbulent features at the two different evolution stages is complemented by a theoretical description based on the turbulence transport model equations for nearly incompressible magnetohydrodynamics. The results provide strong evidence that the solar wind turbulence already undergoes significant evolution at distances less than 0.3 au from the Sun, which can be satisfactorily explained as due to evolving slab fluctuations. This work represents a step forward in understanding the processes that control the transition from weak to strong turbulence in the solar wind and in properly modeling the heliosphere. 

This work presents an analysis of seasonal variations of medium‐scale perturbations (∼500 to ∼5,700 km) spanning altitudes from 90 to 250 km using temperature and wind measurements made by the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument onboard the Ionospheric Connection Explorer (ICON) in the latitude range of 0°–40°N during 2020–2021. Both medium‐scale perturbations (MSP) in temperature and winds below ∼120 km show semi‐annual variations, whereas annual variations of MSP for winds become dominant between 160 and 250 km. The largest wind MSP was observed at ∼110–120 km throughout the year. Spatial variations of MSP at 90–250 km do not show clear geographic patterns in either temperature or wind. Our analysis suggests both seasonal variations of MSP between 90 and 250 km altitudes are influenced by variation on both the sources of MSP and changes in the background wind.

 

The Pamir gneiss domes represent the most extensive exposure of mid to lower crustal rocks in the Himalayan‐Tibetan orogen north of the India‐Asia suture zone. Unlike other domes in the Central and Southern Pamir, the Muztaghata dome stands out due to its higher metamorphic grade, more complex structural elements, and variable timing of metamorphism. In order to unravel the P‐T‐t history of the Muztaghata dome and better constrain the timing of peak metamorphism, we applied petrologic modeling in concert with geochronology to samples from the structure. The Muztaghata gneiss dome is composed of a structurally higher metapelite‐dominated terrane in the west and a structurally lower orthogneiss terrane in the east. Our results from the western terrane indicate high‐pressure eclogite facies peak conditions of ~800°C/22 kbar at ~25–20 Ma. Zircon grains from metapelitic samples from the western terrane also yield Early Jurassic metamorphic U‐Pb ages with REE signals that indicate coeval garnet growth. Our results from the eastern terrane record high‐pressure amphibolite facies peak conditions of ~650°C/14 kbar at ~24–20 Ma, noticeably lower than the structurally higher western terrane indicating structural juxtaposition during Miocene exhumation. Peak metamorphic conditions from the eastern terrane indicate depths below the current Moho, supporting the interpretation that the Early Miocene Pamir crust was thicker than present. This was followed by rapid exhumation from depths of ~75–80 km and partial westward collapse of the Pamir after 20 Ma, possibly driven in part by regional lithospheric delamination.