Search

The Space Weather Investigation Frontier (SWIFT) mission will aim at making major discoveries on the three-dimensional structure and dynamics of heliospheric structures that drive space weather. The focus will be on Interplanetary Coronal Mass Ejections (ICMEs) that originate from massive expulsions of plasma and magnetic flux from the solar corona. They cause the largest geomagnetic storms and solar energetic particle events, threatening to endanger life and disrupt technology on Earth and in space. A big current problem, both regarding fundamental solar-terrestrial physics and space weather, is that we do not yet understand spatial characteristics and temporal evolution of ICMEs and that the existing remote-sensing and in-situ observatories are not suited for resolving multi-layered and evolutionary structures in these massive storm drivers. Here, we propose a groundbreaking mission concept study using solar sail technology that, for the first time, will make continuous, in-situ multi-point observations along the Sun-Earth line beyond the Lagrange point L1 (sub-L1). This unique position, in combination with L1 assets, will allow distinguishing between local and global processes, spatial characteristics, temporal evolution, and particle energization mechanisms related to ICMEs. In addition, measurements of the magnetic field in earthbound ICMEs and their sub-structures from the SWIFT location will double the current forecasting lead-times from L1. This concept also paves the way for missions with increasingly longer forecasting lead-times, addressing NASA and NOAA’s space weather goals, as set forth by the Decadal Survey. The objective of this communication is to inform the community of the ongoing effort, including plans to further develop the mission concept, supported by the Heliophysics Flight Opportunities Studies (HFOS) program under NASA’s Research Opportunities in Space and Earth Sciences (ROSES).

On 2022 February 15–16, multiple spacecraft measured one of the most intense solar energetic particle (SEP) events observed so far in Solar Cycle 25. This study provides an overview of interesting observations made by multiple spacecraft during this event. Parker Solar Probe (PSP) and BepiColombo were close to each other at 0.34–0.37 au (a radial separation of ∼0.03 au) as they were impacted by the flank of the associated coronal mass ejection (CME). At about 100° in the retrograde direction and 1.5 au away from the Sun, the radiation detector on board the Curiosity surface rover observed the largest ground-level enhancement on Mars since surface measurements began. At intermediate distances (0.7–1.0 au), the presence of stream interaction regions (SIRs) during the SEP arrival time provides additional complexities regarding the analysis of the distinct contributions of CME-driven versus SIR-driven events in observations by spacecraft such as Solar Orbiter and STEREO-A, and by near-Earth spacecraft like ACE, SOHO, and WIND. The proximity of PSP and BepiColombo also enables us to directly compare their measurements and perform cross-calibration for the energetic particle instruments on board the two spacecraft. Our analysis indicates that energetic proton measurements from BepiColombo and PSP are in reasonable agreement with each other to within a factor of ∼1.35. Finally, this study introduces the various ongoing efforts that will collectively improve our understanding of this impactful, widespread SEP event.

We present analyses of 0.05–2 MeV ions from the 2022 February 16 energetic storm particle event observed by Parker Solar Probe's (PSP) IS⊙IS/EPI-Lo instrument at 0.35 au from the Sun. This event was characterized by an enhancement in ion fluxes from a quiet background, increasing gradually with time with a nearly flat spectrum, rising sharply near the arrival of the coronal mass ejection (CME)–driven shock, becoming nearly a power-law spectrum, then decaying exponentially afterward, with a rate that was independent of energy. From the observed fluxes, we determine diffusion coefficients, finding that far upstream of the shock the diffusion coefficients are nearly independent of energy, with a value of 10 ^20 cm ^2 s ^−1 . Near the shock, the diffusion coefficients are more than 1 order of magnitude smaller and increase nearly linearly with energy. We also determine the source of energetic particles, by comparing ratios of the intensities at the shock to estimates of the quiet-time intensity to predictions from diffusive shock acceleration theory. We conclude that the source of energetic ions is mostly the solar wind for this event. We also present potential interpretations of the near-exponential decay of the intensity behind the shock. One possibility we suggest is that the shock was overexpanding when it crossed PSP and the energetic particle intensity decreased behind the shock to fill the expanding volume. Overexpanding CMEs could well be more common closer to the Sun, and this is an example of such a case.

We present Solar Orbiter energetic particle observations of two ^3 He-rich events with features more clearly observed than in prior studies. The event of 2022 November 9 observed from 0.59 au contained hundreds of ultraheavy (UH; mass >78 amu) ions whereas previous observations at 1 au have shown only an occasional count or two. The event of 2023 April 8 observed from 0.29 au fortuitously had very low ambient activity, making it possible to observe spectra from the ^3 He acceleration mechanism without contamination, revealing extremely low H and ^4 He intensities arriving simultaneously with other ions observed in typical ^3 He-rich events. Taken together with previous studies, we believe these data show that ^3 He-rich events have a single acceleration mechanism that is responsible for the unique abundance features of ^3 He, heavy ions, and UH ions. Considering the acceleration model of Roth & Temerin that heats the ions over a broad range of gyrofrequencies away from those damped by H and ^4 He, we calculate reasonable fits to the observed abundances O–Fe. A key result is that high values of, e.g., Fe/O typical of such events is not due to preferential Fe heating, but on the contrary is due mainly to the depletion of O, which at elevated temperatures has a charge-to-mass ratio in the region of the waves damped by ^4 He. The model also naturally incorporates features of high-ionization states and neutron-rich isotope enhancements that have been long-standing puzzles in observations of this type of flare.

During the thirteenth encounter of the Parker Solar Probe (PSP) mission, the spacecraft traveled through a topologically complex interplanetary coronal mass ejection (ICME) beginning on 2022 September 5. PSP traversed through the flank and wake of the ICME while observing the event for nearly two days. The Solar Probe ANalyzer and FIELDS instruments collected in situ measurements of the plasma particles and magnetic field at ∼13.3 R _S from the Sun. We observe classical ICME signatures, such as a fast-forward shock, bidirectional electrons, low proton temperatures, low plasma β , and high alpha particle to proton number density ratios. In addition, PSP traveled through two magnetic inversion lines, a magnetic reconnection exhaust, and multiple sub-Alfvénic regions. We compare these in situ measurements to remote-sensing observations from the Wide-field Imager for Solar PRobe Plus instrument on board PSP and the Sun Earth Connection Coronal and Heliospheric Investigation on the Solar Terrestrial Relations Observatory. Based on white-light coronagraphs, two CMEs are forward modeled to best fit the extent of the event. Furthermore, Air Force Data Assimilative Flux Transport magnetograms modeled from Global Oscillation Network Group magnetograms and Potential Field Source Surface modeling portray a global reconfiguration of the heliospheric current sheet (HCS) after the CME event, suggesting that these eruptions play a significant role in the evolution of the HCS.

We analyze periods with elevated >40 MeV proton intensities observed near Earth over a time span of 43 yr (1973–2016) that coincide with the passage of interplanetary (IP) shocks. Typically, elevated proton intensities result from large solar energetic particle (SEP) events. The IP shocks observed during these elevated-intensity periods may or may not be related to the origin of the SEP events. By choosing those cases when the shocks can be confidently associated with the solar eruption that generated the SEP event, we analyze the components of these SEP events that are localized in the vicinity of the shock (so-called “energetic storm particles”, ESPs), focusing on those events where the ESP component exceeds 40 MeV. We examine the interdependence of these high-energy ESPs with (i) the properties of the solar eruptions that generated the shocks and the SEP events, and (ii) the parameters of the shocks at their arrival at 1 au. The solar eruptions at the origin of the shocks producing >40 MeV proton ESP intensity enhancements are within ±50° longitude of central meridian and are associated with fast coronal mass ejections (plane-of-sky speeds ≳1000 km s ^−1 ). The ESP events with the largest >40 MeV proton intensity increases tend to occur when there are structures such as intervening IP coronal mass ejections and other unrelated shocks present in the solar wind through which the shock is propagating. Among the various local shock parameters considered, only the shock speed shows a certain degree of correlation with the observed ESP intensity increase.

We have developed aran04 a tool for rapid predictions of proton flux and fluence profiles observed during gradual solar energetic particle (SEP) events and upstream of the associated traveling interplanetary shocks. This code, named SOLPENCO (for SOLar Particle ENgineering COde), contains a data base with a large set of interplanetary scenarios under which SEP events develop. These scenarios are basically defined by the solar longitude of the parent solar activity, ranging from E75 to W90, and by the position of the observer, located at 0.4 AU or at 1.0 AU, from the Sun. We are now analyzing the performance and reliability of SOLPENCO. We address here two features of SEP events especially relevant to space weather purposes: the peak flux and the fluence. We analyze how the peak flux and the fluence of the synthetic profiles generated by SOLPENCO vary as a function of the strength of the CME-driven shock, the heliolongitude of the solar parent activity and the particle energy considered. In particular, we comment on the dependence of the fluence on the radial distance of the observer (which does not follow an inverse square law), and we draw conclusions about the influence of the shock as a particle accelerator in terms of its evolving strength and the heliolongitude of the solar site where the SEP event originated.

We study the variability of the heliospheric energetic proton-to-helium abundance ratios during different phases of the solar cycle. We use energetic particle, solar wind, and magnetic field data from the Ulysses, ACE and IMP-8 spacecraft to compare the H/He intensity ratio at high heliographic latitudes and in the ecliptic plane. During the first out-of-ecliptic excursion of Ulysses (1992–1996), the HI-SCALE instrument measured corotating energetic particle intensity enhancements characterized by low values (< 10) of the 0.5–1.0 MeV nucleon-1 H/He intensity ratio. During the second out-of-ecliptic excursion of Ulysses (1999–2002), the more frequent occurrence of solar energetic particle events resulted in almost continuously high (< 20) values of the H/He ratio, even at the highest heliolatitudes reached by Ulysses. Comparison with in-ecliptic measurements from an identical instrument on the ACE spacecraft showed similar H/He values at ACE and Ulysses, suggesting a remarkable uniformity of energetic particle intensities in the solar maximum heliosphere at high heliolatitudes and in the ecliptic plane. In-ecliptic observations of the H/He intensity ratio from the IMP-8 spacecraft show variations between solar maximum and solar minimum similar to those observed by Ulysses at high heliographic latitudes. We suggest that the variation of the H/He intensity ratio throughout the solar cycle is due to the different level of transient solar activity, as well as the different structure and duration that corotating solar wind structures have under solar maximum and solar minimum conditions. During solar minimum, the interactions between the two different types of solar wind streams (slow vs. fast) are strong and long-lasting, allowing for a continuous and efficient acceleration of interstellar pickup He +. During solar maximum, transient events of solar origin (characterized by high values of the H/He ratio) are able to globally fill the heliosphere. In addition, during solar maximum, the lack of strong recurrent high-speed solar wind streams, together with the dynamic character of the Sun, lead to weak and short-lived solar wind stream interactions. This results in a less efficient acceleration of pickup He +, and thus a higher value of the H/He intensity ratio.Key words. Interplanetary physics (energetic particles, interplanetary shocks; solar wind plasma)

Abstract Background Previous studies have reported that periderm (the outer ectodermal layer) in zebrafish partially expands into the mouth and pharyngeal pouches, but does not reach the medial endoderm, where the pharyngeal teeth develop. Instead, periderm-like cells, arising independently from the outer periderm, cover prospective tooth-forming epithelia and are crucial for tooth germ initiation. Here we test the hypothesis that restricted expansion of periderm is a teleost-specific character possibly related to the derived way of early embryonic development. To this end, we performed lineage tracing of the periderm in a non-teleost actinopterygian species possessing pharyngeal teeth, the sterlet sturgeon (Acipenser ruthenus), and a sarcopterygian species lacking pharyngeal teeth, the axolotl (Ambystoma mexicanum). Results In sturgeon, a stratified ectoderm is firmly established at the end of gastrulation, with minimally a basal ectodermal layer and a surface layer that can be homologized to a periderm. Periderm expands to a limited extent into the mouth and remains restricted to the distal parts of the pouches. It does not reach the medial pharyngeal endoderm, where pharyngeal teeth are located. Thus, periderm in sturgeon covers prospective odontogenic epithelium in the jaw region (oral teeth) but not in the pharyngeal region. In axolotl, like in sturgeon, periderm expansion in the oropharynx is restricted to the distal parts of the opening pouches. Oral teeth in axolotl develop long before mouth opening and possible expansion of the periderm into the mouth cavity. Conclusions Restricted periderm expansion into the oropharynx appears to be an ancestral feature for osteichthyans, as it is found in sturgeon, zebrafish and axolotl. Periderm behavior does not correlate with presence or absence of oral or pharyngeal teeth, whose induction may depend on ‘ectodermalized’ endoderm. It is proposed that periderm assists in lumenization of the pouches to create an open gill slit. Comparison of basal and advanced actinopterygians with sarcopterygians (axolotl) shows that different trajectories of embryonic development converge on similar dynamics of the periderm: a restricted expansion into the mouth and prospective gill slits.

In this study, the removal of cadmium (Cd) by free-living Oscillatoria sp. was studied. Our results showed that maximal Cd removal efficiency (~60%) by the cyanobacterial culture was achieved within 12–24 h in the presence of 5.0 or 25.0 mg/L of Cd. The mechanisms underlying this phenomenon were explored by elemental analysis and FTIR-ATR spectroscopy. It was found that metal adsorption by negatively charged functional groups in the cyanobacterial biomass was the main mechanism used by Oscillatoria sp. to remove metal from the aqueous medium, followed by Cd bioaccumulation into living cells. Additionally, Cd-exposed microalgae showed increased oxidative stress (MDA formation), a decreased dehydrogenase activity, a higher amount of soluble carbohydrates and a decreased total carotenoid concentration, as compared to the control cells. These results suggest that Oscillatoria sp. improved its antioxidative defense system under stressful conditions, through carotenoid-mediated ROS quenching and induction of carbohydrate catabolism, in order to counteract the oxidative damage and preserve the photosynthetic machinery and cellular energetics. In fact, no significant reduction in Oscillatoria sp. cell density, total protein amount, and chlorophyll a content was observed after 24-h Cd exposure, even at the highest metal concentration tested (i.e., 25.0 mg/L). Hence, the presented results are the first to describe some new insights about the metabolic and physiological behavior of living Oscillatoria sp. during Cd remediation, and open up the possibility of finding an equilibrium that maximizes metal removal performance with an active cyanobacterial metabolism, to achieve a rewarding and sustainable management of industrial metal-polluted wastewater.