Sodium Tail Research Articles

Fine-scale structure in cometary dust tails II: Further evidence for a solar wind influence on cometary dust dynamics from the analysis of striae in comet C/2011 L4 Pan-STARRS

Striated features, or striae, form in cometary dust tails due to an as-yet not fully constrained process or processes. Using STEREO-B SECCHI HI-1 instrument data, we display the evolution of striae in the tail of C/2011 L4 Pan-STARRS over a period of 8 days. This includes a period of morphological changes on 2013 March 14–15, similar to the reorganisation of striae previously observed in the tail of C/2006 P1 McNaught. This reorganisation is again attributed to Lorentz forces caused by the comet’s dust tail crossing the heliospheric current sheet. We further analyse the alignments of reorganised striae at both C/2006 P1 and C/2011 L4 and show these alignments have mixed compatibility with an additional solar wind influence. We also report the discovery of a bright neutral sodium tail at C/2011 L4.

The 2022 encounter of the outburst material from comet 73P/Schwassmann–Wachmann 3

ABSTRACT The encounter of the meteoric material from 73P/Schmassmann–Wachmann 3 produced during the comet’s 1995 outburst in May 2022 provides a rare and valuable opportunity to understand a fragmenting comet. Here, we explore various ejection configurations and their impact on the meteor outburst detected in the early hours of ut 2022 May 31. We show that the dust must have been ejected ∼4 to 5× faster than calculated by water-ice sublimation model to best match the observed meteor activity. As only a small subset of particles with a narrow range of cross-section is expected to have reached the Earth, the large spread of meteor brightness likely indicates the presence of large but porous meteoroids in the trail. Other effects such as an enhanced lunar sodium tail and a visible glow from the meteoroid trail may have also occurred during the encounter.

Diagnostic Simulations of the Lunar Sodium Tail and Bright Spot

AbstractNumerical simulations of the lunar sodium tail and its bright sodium spot are presented. As an attempt to do reverse engineering to understand the lunar sodium exosphere, we simulated velocity distributions of the sodium tail and its bright spot that emerges in the night sky around new Moon phases. In this work, three physical sodium sources (i.e., photon‐stimulated desorption [PSD], solar‐wind ion sputtering [SIS], meteor impact vaporization [MIV]), the dust anisotropy effect reported by Lunar Atmosphere and Dust Environment Explorer (LADEE), three gravitational sources (i.e., the Moon, the Earth, and the Sun), and variable solar radiation pressure effects are considered. We simulated velocity distributions of the lunar bright spot considering different source contribution ratios and their temperatures in order to find the best initial parameters which can account for the important observed recessional velocity of 12.4 km/s by Mierkiewicz et al. (2006, https://doi.org/10.1029/2006GL027650). We found that the upper limits of Maxwellian temperatures of 1,800 K for the PSD and 2,500 K for the MIV and that the best contribution ratio of the three major sodium sources (i.e., PSD: SIS: MIV) is found at the case of 2: 1: 3 (i.e., MIV dominant). Based on the previous brightness observations of the bright spot, the total production rate of the lunar sodium is estimated to usually vary between 0.4 and 1.3 × 1022/s. We introduce an interesting event in the lunar sodium tail, the Sodium Ring phenomena, which can occur transiently during the total solar eclipse due to the umbra and penumbra effects of the Earth.

Long‐Term Observations and Physical Processes in the Moon's Extended Sodium Tail

AbstractThe lunar surface is constantly bombarded by the solar wind, photons, and meteoroids, which can liberate Na atoms from the regolith. These atoms are subsequently accelerated by solar photon pressure to form a long comet‐like tail opposite the sun. Near new moon, these atoms encounter the Earth's gravity and are “focused” into a beam of enhanced density. This beam appears as the ∼3° diameter Sodium Moon Spot (SMS). Data from the all sky imager at the El Leoncito Observatory have been analyzed for changes in the SMS shape and brightness. New geometry‐based relationships have been found that affect the SMS brightness. The SMS is brighter when the Moon is north of the ecliptic at new moon; the SMS is brighter when new moon occurs near perigee; and the SMS peaks in brightness ∼5 h after new moon. After removing these effects, the data were analyzed for long term and seasonal patterns that could be attributed to changes in source mechanisms. No correlation was found between the SMS brightness and the 11‐year solar‐cycle, the proton or the He++ flow pressure, the density, the speed or the plasma temperature of the solar wind, but an annual pattern was found. A ∼0.83 correlation (Pearson's “r”) was found between the SMS brightness and a 4‐year average of sporadic meteor rates at Earth, suggesting a cause‐and‐effect. The new insights gained from this long‐term study put new constraints on the variability of the potential sources of the Na atoms escaping from the Moon.

Long-Term Observations and Physical Processes in the Moon's Extended Sodium Tail

Long-Term Observations and Physical Processes in the Moon's Extended Sodium Tail

Long-Term Observations and Physical Processes in the Moon's Extended Sodium Tail

Long-Term Observations and Physical Processes in the Moon's Extended Sodium Tail

Space Weathering of Super-Earths: Model Simulations of Exospheric Sodium Escape from 61 Virgo b

Abstract Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape is well traced by sodium atoms scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, sodium atoms are released from surface regolith. Some of these released sodium atoms are escaping from Mercury’s gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure. We expect similar phenomena on exoplanets. The hot super-Earth 61 Vir b orbiting a G3V star at only 0.05 au may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. Here, we performed model simulations for Mercury (to verify our model) and 61 Vir b as a representative super-Earth. We have found that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts, to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. Our model suggests that 61 Vir b seems to have an exo-base atmosphere like that of Mercury.

The first long-term all-sky imager observation of lunar sodium tail

The Moon possesses a long tail of neutral sodium atoms that are emitted from the lunar surface and transported anti-sunward by the solar radiation pressure. Since the earth crosses the lunar sodium tail for a few days around the new moon, the resonant light emission from sodium atoms can be detected from the ground. Here we show the first long-term (16 years) observation of the lunar sodium tail, using an all-sky imager at Shigaraki Observatory (35°N, 136°E), Japan. We have surveyed our database of all-sky sodium images at a wavelength of 589.3 nm to find more than 20 events in which a bright spot emerges around the anti-lunar point during the new moon periods. We could not find any clear correlation between the sodium brightness and solar wind parameters (density, speed, dynamic pressure, and F10.7 index). In particular, no enhancement of the sodium spot brightness is detected even under very high density solar wind conditions (70 cm−3; an order-of-magnitude higher than usual), which means that solar wind sputtering is not a principal mechanism of the formation of the lunar sodium tail.

Synthetic pyrethroids (Type II) and freshwater fish culture: Perils and mitigations

As a new class of agricultural insecticides, synthetic pyrethroids are widely used to control insect pests. Synthetic pyrethroids have been shown to enter the aquatic environment from agricultural runoff or drift from aerial and ground-based spraying applications posing threat to fishes which are less tolerant to pesticides through direct exposure. These insecticides interfere with the sodium channel of the nervous system resulting in prolonged sodium tail current. Widespread application of these chemicals has warranted the attention of the ecologist to understand the impact of these chemicals on the aquatic environment. In this perspective, an updated account of toxicological evaluation of three type II synthetic pyrethroids, viz. deltamethrin, cypermethrin and fenvalerate in terms of their physico-chemical, metabolic, hematological, histological, behavioral and reproductive aspects with respect to the fishes has been presented which may be useful for policy makers, academics, environmental scientists and agricultural professionals needing ready access to this information. The aim of the present synoptic literature appraisal was to summarize the main effect of current use, type II synthetic pyrethroids (deltamethrin, cypermethrin and fenvalerate) on aquatic environment due to their persistence and accumulation. This article will focus on non-target organisms in inland fresh water environment with special reference to fin fishes and will critically evaluate the toxicity of these pyrethroids in terms of growth inhibition, metabolic disorders, neurotoxicity, reproductive failure, enzymatic dysfunction, haematological alterations, and tissue damages. The rationalized information in this milieu may be useful in ecological risk evaluation and human health management as fish serves as an important bio-indicator for aquatic systems health.

NEUTRAL Na IN COMETARY TAILS AS A REMNANT OF EARLY AQUEOUS ALTERATION

Observations of comet C/1995O1 Hale-Bopp during the spring of 1997 led to the discovery of a neutral sodium tail whose origin is still not clearly understood. Here, we propose an interpretation for the origin of this sodium tail, which is based upon chemical grounds. Starting from Na+ trapped chemically during the condensation of refractory material in the protosolar nebula to its incorporation in the building blocks of comets and its transfer from refractory to volatile phases in the nucleus due to aqueous alteration, we follow the chemical path of sodium until its transformation into a neutral atom when released from the sublimating cometary ice. We propose that two Na reservoirs should coexist in a comet: one coming from the refractory dust, the other one from the icy matrix. Their relative importance would depend on the extent of the zone where liquid water formed within the nucleus and the time during which water remained liquid, thus favoring the Na+ exchange between rocks and ice. These two key parameters would in turn strongly depend on the thermal history of the comet (amounts of radiogenic nuclides, orbital history, etc.). If our model is correct, the detection of Na originating from water ice would be a testimonial of the past aqueous alteration of the comet or its parent body.

Kinetic modeling of sodium in the lunar exosphere

Our knowledge about the lunar environment is based on a large volume of ground-based, remote, and in situ observations. These observations have been conducted at different times and sampled different pieces of such a complex system as the surface-bound exosphere of the Moon. Numerical modeling is the tool that can link results of these separate observations into a single picture. Being validated against previous measurements, models can be used for predictions and interpretation of future observations results.In this paper we present a kinetic model of the sodium exosphere of the Moon as well as results of its validation against a set of ground-based and remote observations. The unique characteristic of the model is that it takes the orbital motion of the Moon and the Earth into consideration and simulates both the exosphere as well as the sodium tail self-consistently. The extended computational domain covers the part of the Earth’s orbit at new Moon, which allows us to study the effect of Earth’s gravity on the lunar sodium tail.The model is fitted to a set of ground-based and remote observations by tuning sodium source rate as well as values of sticking, and accommodation coefficients. The best agreement of the model results with the observations is reached when all sodium atoms returning from the exosphere stick to the surface and the net sodium escape rate is about 5.3×1022s−1.

Monte Carlo modeling of north‐south asymmetries in Mercury's sodium exosphere

AbstractGround‐based observations and MESSENGER's first flyby show persistent asymmetries in Mercury's neutral sodium tail, with brightest emission often seen in the northern lobe. This feature may be associated with the recent finding that the magnetic dipole moment is offset from the planet's center by 0.2 RM to the north, while approximately aligned with the spin axis. Such a configuration produces an asymmetry in the magnetosphere cusp whereby more plasma has direct access to the planet's southern hemisphere than the north. Using 3‐D numerical modeling, it is demonstrated that ion precipitation, enhanced in the south, can result in the observed Na emission profiles across the tail that are brighter to the north. However, sources located at high‐latitude cusp footprints on the dayside are unable to match the observed width of the brightness profiles across the tail. Instead, these simulations provide evidence for lower latitude sources on the dawnside, resulting from the accumulation of sodium during the long Mercury night. Photodesorption, rather than ion sputtering, is determined to be the responsible mechanism for this population's release and escape from the planet's surface.

Sodium atoms in the lunar exotail: Observed velocity and spatial distributions

The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations measured the average radial velocity of sodium atoms moving down the lunar tail beyond Earth (i.e., near the anti-lunar point) to be ∼12.5km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15°×15° region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights bracketing new Moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3° east along the ecliptic per night. Preliminary modeling results suggest the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution. Future observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days.

Differential state-dependent modification of inactivation-deficient Nav1.6 sodium channels by the pyrethroid insecticides S-bioallethrin, tefluthrin and deltamethrin

Pyrethroid insecticides disrupt nerve function by modifying the gating kinetics of transitions between the conducting and nonconducting states of voltage-gated sodium channels. Pyrethroids modify rat Nav1.6+β1+β2 channels expressed in Xenopus oocytes in both the resting state and in one or more states that require channel activation by repeated depolarization. The state dependence of modification depends on the pyrethroid examined: deltamethrin modification requires repeated channel activation, tefluthrin modification is significantly enhanced by repeated channel activation, and S-bioallethrin modification is unaffected by repeated activation. Use-dependent modification by deltamethrin and tefluthrin implies that these compounds bind preferentially to open channels. We constructed the rat Nav1.6Q3 cDNA, which contained the IFM/QQQ mutation in the inactivation gate domain that prevents fast inactivation and results in a persistently open channel. We expressed Nav1.6Q3+β1+β2 sodium channels in Xenopus oocytes and assessed the modification of open channels by pyrethroids by determining the effect of depolarizing pulse length on the normalized conductance of the pyrethroid-induced sodium tail current. Deltamethrin caused little modification of Nav1.6Q3 following short (10ms) depolarizations, but prolonged depolarizations (up to 150ms) caused a progressive increase in channel modification measured as an increase in the conductance of the pyrethroid-induced sodium tail current. Modification by tefluthrin was clearly detectable following short depolarizations and was increased by long depolarizations. By contrast modification by S-bioallethrin following short depolarizations was not altered by prolonged depolarization. These studies provide direct evidence for the preferential binding of deltamethrin and tefluthrin (but not S-bioallethrin) to Nav1.6Q3 channels in the open state and imply that the pyrethroid receptor of resting and open channels occupies different conformations that exhibit distinct structure–activity relationships.

Actions of tefluthrin on rat Na v1.7 voltage-gated sodium channels expressed in Xenopus oocytes

In rats expression of the Na v1.7 voltage-gated sodium channel isoform is restricted to the peripheral nervous system and is abundant in the sensory neurons of the dorsal root ganglion. We expressed the rat Na v1.7 sodium channel α subunit together with the rat auxiliary β1 and β2 subunits in Xenopus laevis oocytes and assessed the effects of the pyrethroid insecticide tefluthrin on the expressed currents using the two-electrode voltage clamp method. Tefluthrin at 100 μM modified of Na v1.7 channels to prolong inactivation of the peak current during a depolarizing pulse, resulting in a marked “late current” at the end of a 40 ms depolarization, and induced a sodium tail current following repolarization. Tefluthrin modification was enhanced up to twofold by the application of a train of up to 100 5 ms depolarizing prepulses. These effects of tefluthrin on Na v1.7 channels were qualitatively similar to its effects on rat Na v1.2, Na v1.3 and Na v1.6 channels assayed previously under identical conditions. However, Na v1.7 sodium channels were distinguished by their low sensitivity to modification by tefluthrin, especially compared to Na v1.3 and Na v1.6 channels. It is likely that Na v1.7 channels contribute significantly to the tetrodotoxin-sensitive, pyrethroid-resistant current found in cultured dorsal root ganglion neurons. We aligned the complete amino acid sequences of four pyrethroid-sensitive isoforms (house fly Vssc1; rat Na v1.3, Na v1.6 and Na v1.8) and two pyrethroid-resistant isoforms (rat Na v1.2 and Na v1.7) and found only a single site, located in transmembrane segment 6 of homology domain I, at which the amino acid sequence was conserved among all four sensitive isoform sequences but differed in the two resistant isoform sequences. This position, corresponding to Val410 of the house fly Vssc1 sequence, also aligns with sites of multiple amino acid substitutions identified in the sodium channel sequences of pyrethroid-resistant insect populations. These results implicate this single amino acid polymorphism in transmembrane segment 6 of sodium channel homology domain I as a determinant of the differential pyrethroid sensitivity of rat sodium channel isoforms.

Three-dimensional simulations of the lunar sodium exosphere and its tail

[1] The brightness distributions of the lunar sodium exosphere reported by Flynn and Mendillo (1993) and the receding velocities of the lunar sodium tail observed by Mierkiewicz et al. (2006) are reproduced by 3-D Monte Carlo simulations. We consider the effects of two spatially different sodium sources simultaneously: dayside source with the dependency of solar zenith angle and an isotropic source due to micrometeoroid impact. In the simulations, the following effects are taken into account: (1) the gravity of the Moon, the Earth, and the Sun with the orbital motion of the Moon; (2) photoionizations, solar radiation pressure, and returns to the lunar surface; and (3) the shadows of the Earth and Moon. The sodium brightness observed by Flynn and Mendillo (1993) is successfully modeled, from which the most probable source ratio between the isotropic and dayside sources is estimated to be 70%∼80%: 30%∼20%, respectively. The best coma model provides an initial velocity of 2.0 km/s with a narrow Doppler width of 0.2 km/s and a total production rate of 0.7 × 1022/s. On the basis of the best 3-D lunar coma model, we also simulate the receding velocity distribution of lunar sodium tail, and we find satisfactory models for high receding velocity and its wide dispersion observed by Mierkiewicz et al. (2006) considering the effect of variable solar radiation pressure and appropriate ionization times.

Comet-like tail-formation of exospheres of hot rocky exoplanets: Possible implications for CoRoT-7b

In this study, the interaction of stellar wind plasma with the exosphere and possibly with the planetary magnetospheric environment of close-in rocky exoplanets is investigated. In particular, we focus on the “super-Earth” CoRoT-7b, which has been recently discovered by the CoRoT space observatory. The physical properties of such a planet, with an orbital distance of about 0.017 AU from its host star, may most likely resemble a big and more massive Mercury-type planet in the sense that it most likely releases its surface elements into space. Based on the present knowledge of CoRoT-7b and drawing on the analogy to Solar System planets, we use numerical models to simulate exospheric and magnetospheric distributions of different particle populations, among which are neutral sodium and ionised calcium and magnesium. We find that, for most species, the atmospheric loss rate in such an extreme environment can be very high, so that a neutral and an ionised tail of escaping particles will form. Depending on the planetary composition we postulate the presence of a sodium tail, similar to that of Mercury but shorter due to the shorter Na lifetime, and of an extended magnetospheric distribution of ionised calcium or magnesium. The feasibility of observation of such populations is also discussed.

Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Na v1.6 sodium channels

We expressed rat Na v1.6 sodium channels in combination with the rat β 1 and β 2 auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 μM), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were ~ 9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 μM), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 μM), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration–effect data showed that repetitive depolarization increased the potency of tefluthrin ~ 15-fold and that tefluthrin was ~ 10-fold more potent than deltamethrin as a use-dependent modifier of Na v1.6 sodium channels. Concentration–effect data from parallel experiments with the rat Na v1.2 sodium channel coexpressed with the rat β 1 and β 2 subunits in oocytes showed that the Na v1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Na v1.2 isoform. These results implicate sodium channels containing the Na v1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.

Orbital effects on Mercury’s escaping sodium exosphere

We present results from coronagraphic imaging of Mercury’s sodium tail over a 7° field of view. Several sets of observations made at the McDonald Observatory since May 2007 show a tail of neutral sodium atoms stretching more than 1000 Mercury radii (R m) in length, or a full degree of sky. However, no tail was observed extending beyond 120 R m during the January 2008 MESSENGER fly-by period, or during a similar orbital phase of Mercury in July 2008. Large changes in Mercury’s heliocentric radial velocity cause Doppler shifts about the Fraunhofer absorption features; the resultant change in solar flux and radiation pressure is the primary cause of the observed variation in tail brightness. Smaller fluctuations in brightness may exist due to changing source rates at the surface, but we have no explicit evidence for such changes in this data set. The effects of radiation pressure on Mercury’s escaping atmosphere are investigated using seven observations spanning different orbital phases. Total escape rates of atmospheric sodium are estimated to be between 5 and 13 × 10 23 atoms/s and show a correlation to radiation pressure. Candidate sources of Mercury’s sodium exosphere include desorption by UV sunlight, thermal desorption, solar wind channeled along Mercury’s magnetic field lines, and micro-meteor impacts. Wide-angle observations of the full extent of Mercury’s sodium tail offer opportunities to enhance our understanding of the time histories of these source rates.

The sodium tail of the Moon

During the few days centered about new Moon, the lunar surface is optically hidden from Earth-based observers. However, the Moon still offers an observable: an extended sodium tail. The lunar sodium tail is the escaping “hot” component of a coma-like exosphere of sodium generated by photon-stimulated desorption, solar wind sputtering and meteoroid impact. Neutral sodium atoms escaping lunar gravity experience solar radiation pressure that drives them into the anti-solar direction forming a comet-like tail. During new Moon time, the geometry of the Sun, Moon and Earth is such that the anti-sunward sodium flux is perturbed by the terrestrial gravitational field resulting in its focusing into a dense core that extends beyond the Earth. An all-sky camera situated at the El Leoncito Observatory (CASLEO) in Argentina has been successfully imaging this tail through a sodium filter at each lunation since April 2006. This paper reports on the results of the brightness of the lunar sodium tail spanning 31 lunations between April 2006 and September 2008. Brightness variability trends are compared with both sporadic and shower meteor activity, solar wind proton energy flux and solar near ultra violet (NUV) patterns for possible correlations. Results suggest minimal variability in the brightness of the observed lunar sodium tail, generally uncorrelated with any single source, yet consistent with a multi-year period of minimal solar activity and non-intense meteoric fluxes.