Rotational Bursting Research Articles

ENIGMATIC NEBULOUS COMPANIONS TO THE GREAT SEPTEMBER COMET OF 1882 AS SOHO-LIKE KREUTZ SUNGRAZERS CAUGHT IN TERMINAL OUTBURST

I investigate the nature of the transient nebulous companions to the sungrazing comet C/1882 R1, known as the Great September Comet. The features were located several degrees to the southwest of the comet's head and reported independently by four observers, including J.F.J. Schmidt and E.E. Barnard, over a period of ten days nearly one month after perihelion, when the comet was 0.7 AU to 1 AU from the Sun. I conclude that none of the nebulous companions was ever sighted more than once and that, contrary to his belief, Schmidt observed unrelated objects on the four consecutive mornings. Each nebulous companion is proposed to have been triggered by a fragment at most a few tens of meters across, released from the comet's nucleus after perihelion and seen only because it happened to be caught in the brief terminal outburst, when its mass was suddenly shattered into a cloud of mostly microscopic debris due possibly to rotational bursting triggered by sublimation torques. The fragment's motion was affected by a strong outgassing-driven nongravitational acceleration with a significant out-of-plane component. Although fragmentation events were common, only a small fraction of nebulous companions was detected because of their transient nature. The observed brightness of the nebulous companions is proposed to have been due mainly to C2 emissions, with a contribution from scattering of sunlight by the microscopic dust. By their nature, the fragments responsible for the nebulous companions bear a strong resemblance to the dwarf Kreutz sungrazers detected with the coronagraphs aboard the SOHO space probe. Only their fragmentation histories are different and the latter display no terminal outburst, a consequence of extremely short lifetimes of the sublimating icy and refractory material in the Sun's corona.

Direct-Pathway Spiny Projection Neuron Inhibition Evokes Transient Circuit Imbalance Manifested as Rotational Behavior

The striatum collects and integrates information from many different areas of the brain and propels this forward to the basal ganglia (BG) output structures. In this way, the striatum is playing a pivotal role in control of voluntary movements and is implicated in debilitating movement disorders such as Parkinson’s disease. The functional backbone of the striatum is represented by direct pathway (dSPN) Drd1-expressing and indirect pathway (iSPN) Drd2-expressing spiny projection neurons (SPN), exerting opposite effects on movement. In rodent models of striatal function, unilateral dopamine deprivation is known to induce ipsilateral rotational behavior. To further study imbalance of the BG circuit and striatal domain influence on behavioral outcome, we employed a viral approach based on tetanus toxin light chain (TeLC) activity for permanent inhibition of dSPN activity in dorsomedial striatum (DMS). Cre-dependent TeLC injected unilaterally into the DMS of Drd1-Cre mice resulted in robust expression of TeLC in the dSPN cell populations as shown by immunohistochemistry. In the TeLC expressing mice, but not in control mice, we observed ipsilateral rotations that were enhanced upon administration of amphetamine to augment striatal dopamine levels. We argue that the observed single turns of ipsilateral rotations occur because of TeLC-mediated silencing of dSPN activity in one hemisphere, causing unresponsiveness to dopamine transients during movement initiation. This evokes a temporal BG circuit imbalance manifested as short bursts of rotations, particular evident during extrinsic dopaminergic modulation.

Outburst and Splitting of Interstellar Comet 2I/Borisov

Abstract We present Hubble Space Telescope observations of a photometric outburst and splitting event in interstellar comet 2I/Borisov. The outburst, first reported with the comet outbound at ∼2.8 au, was caused by the expulsion of solid particles having a combined cross section ∼100 km2 and a mass in 0.1 mm sized particles ∼2 × 107 kg. The latter corresponds to ∼10−4 of the mass of the nucleus, taken as a sphere of radius 500 m. A transient “double nucleus” was observed on UT 2020 March 30 (about 3 weeks after the outburst), having a cross section ∼0.6 km2 and corresponding dust mass ∼105 kg. The secondary was absent in images taken on and before March 28 and in images taken on and after April 3. The unexpectedly delayed appearance and rapid disappearance of the secondary are consistent with an origin through rotational bursting of one or more large (meter-sized) boulders under the action of outgassing torques, following their ejection from the main nucleus. Overall, our observations reveal that the outburst and splitting of the nucleus are minor events involving a negligible fraction of the total mass: 2I/Borisov will survive its passage through the planetary region largely unscathed.

Chemogenetic Targeting of Dorsomedial Direct-pathway Striatal Projection Neurons Selectively Elicits Rotational Behavior in Mice

The striatum of the basal ganglia is pivotal for voluntary movements and is implicated in debilitating movement disorders such as Parkinsonism and dystonia. Striatum projects to downstream nuclei through direct (dSPN) and indirect (iSPN) pathway projection neurons thought to exert opposite effects on movement. In rodent models of striatal function, unilateral dopamine deprivation induces ipsiversive rotational behavior. The dSPNs of the dorsal striatum are believed to engage distinct motor programs but underlying mechanisms remain unclear. Here, we show by employing chemogenetics [Designer Receptors Exclusively Activated by Designer Drugs (DREADDs)] that unilateral inhibition of dorsomedial dSPNs is sufficient to selectively impair contraversive movement and elicit ipsiversive rotational behavior in mice. Adeno-associated virus (AAV) encoding Cre-dependent Gi-coupled DREADD was injected unilaterally into the dorsomedial striatum of Drd1-Cre mice, resulting in expression of the modified human M4 muscarinic receptor (hM4Di) in ∼20% of dorsostriatal dSPNs. Upon hM4Di activation, a striking positive linear correlation was found between turn ratio and viral expression, which corroborates a relationship between unilateral inhibition of dorsomedial dSPNs and rotational behavior. Bursts of ipsiversive rotations were interspersed with normal ambulation. However, partial unilateral inhibition of ∼20% of dorsostriatal dSPNs did not affect horizontal and vertical locomotion or forelimb use preference. Overall, our results substantiate a unique role of dSPNs in promoting response bias in rotational behavior and show this to be a highly sensitive measure of dSPN performance.

Numerical simulations of rotational bursting of F-coronal dust in eccentric orbits due to coronal mass ejections

Model calculations were carried out to determine the extent of the effects on the rotational bursting of F-coronal dust in eccentric orbits due to their interaction with the flow of coronal mass ejections (CMEs). The model included an initial limiting perihelion distance of 8 solar radii ( R S) for all particles used. The parameters of the CMEs (velocity and proton number density) along with the various parameters of the dust particles (size and median density) were taken into consideration. By keeping these parameters the same and varying one of them, it was found that the velocity of the CMEs protons plays a major role in determining at which heliocentric distance the particle bursts. To a lesser degree, the median density of the particle also had a similar effect. Depending on the values of the dust particles orbital eccentricity, limiting sizes of the dust particles were found beyond which the particles do not burst. More particles bursted in regions close to their perihelion passage, however very few particles bursted near 8 R S from which we conclude that the majority of the fragmented particles were outside the F-corona region. The results show that rotational bursting of the dust in eccentric orbits inside the F-corona forces the particles to fragment outside 8 R S.

Numerical simulations of rotational bursting of F-coronal dust in eccentric orbits due to coronal mass ejections

Numerical simulations of rotational bursting of F-coronal dust in eccentric orbits due to coronal mass ejections

Dust Near The Sun

We review the current knowledge and understanding of dust in the inner solar system. The major sources of the dust population in the inner solar system are comets and asteroids, but the relative contributions of these sources are not quantified. The production processes inward from 1 AU are: Poynting-Robertson deceleration of particles outside of 1 AU, fragmentation into dust due to particle-particle collisions, and direct dust production from comets. The loss processes are: dust collisional fragmentation, sublimation, radiation pressure acceleration, sputtering, and rotational bursting. These loss processes as well as dust surface processes release dust compounds in the ambient interplanetary medium. Between 1 and 0.1 AU the dust number densities and fluxes can be described by inward extrapolation of 1 AU measurements, assuming radial dependences that describe particles in close to circular orbits. Observations have confirmed the general accuracy of these assumptions for regions within 30° latitude of the ecliptic plane. The dust densities are considerably lower above the solar poles but Lorentz forces can lift particles of sizes < 5 μm to high latitudes and produce a random distribution of small grains that varies with the solar magnetic field. Also long-period comets are a source of out-of-ecliptic particles. Under present conditions no prominent dust ring exists near the Sun. We discuss the recent observations of sungrazing comets. Future in-situ experiments should measure the complex dynamics of small dust particles, identify the contribution of cometary dust to the inner-solar-system dust cloud, and determine dust interactions in the ambient interplanetary medium. The combination of in-situ dust measurements with particle and field measurements is recommended.

The age of the Geminids: a constraint from the spin-up time-scale

Interpreting fireball flickering in terms of the rotational modulation of the ablation process, the time since ejection into space of three Geminid meteoroids is determined. By estimating the time required to spin-up a meteoroid through non-isotropic photon scattering interactions with the solar radiation field, we find meteoroid ages consistent with ejection times some 1000‐ 4000 yr ago. There appears to be some indication that the stream formation process lasted for at least ∼1000 yr. We also estimate the rotational bursting conditions for the three Geminid meteoroids and find tensile strengths of some 3 × 10 5 Pa. We interpret our results as being supportive of the argument that the parent body to the Geminid stream, (3200) Phaethon, is an aged cometary nucleus.

Fireball flickering: the case for indirect measurement of meteoroid rotation rates

Data collected during the Meteorite Observation and Recovery Program (MORP) indicate that 4% of bright fireballs show a periodic variation or flickering in brightness. The observed flickering frequencies vary from a few Hz to as high as 500 Hz. We interpret the flickering phenomenon in terms of meteoroid rotation. The MORP data does not reveal any apparent correlation between the flickering frequency and the properties of the meteoroid or the atmospheric flow conditions under which ablation is taking place. It is argued that the most likely cause of the flickering phenomenon is the rotational modulation of the cross-section area presented by the meteoroid to the on-coming airflow. A study is made of the Peekskill fireball and it is concluded that the meteoroid was spun-up during its long flight through the Earth's atmosphere, and that its initial brake up was due to rotational bursting. We also argue that the Peekskill event provides the best observational evidence that the flickering phenomenon is truly related to the rotation rate of the impinging meteoroid. We find that the observed rotation rates of the MORP fireballs are clustered just below the allowed limit set by rotational bursting, but argue that this is due to an observational selection effect that mitigates against the detection of low-frequency flickering.

Impact Ejecta Rotational Bursting as a Mechanism for Producing Stable Ida–Dactyl Systems

The existence of Dactyl, the small satellite of asteroid 243 Ida, presents an intriguing paradox: if exposed to the same projectile bombardment as Ida, it should have been disrupted long ago. To solve this paradox, it has been proposed that either Ida (and the entire Koronis family) is relatively young (≈ 100 Myr) or Dactyl has reaccreted many times from its own debris after having been disrupted. Here we propose a third alternative, that is that Dactyl is much younger than Ida and it was formed by rotational bursting of a precursor fragment ejected from Ida after an impact. We discuss some recent experimental results showing that sizable fragments from shattered targets do undergo rotational bursting and are fissioned after traveling over a length of several target diameters; the relative speed between the fission remnants is comparable to the initial ejection velocity. Then we have performed a number of numerical integrations of the orbits of fictitious particles resulting from an assumed rotational bursting event in the gravitational field of Ida; the results show that, depending on the initial conditions, up to several percent of the particles get trapped into stable satellite–like orbits resembling that of Dactyl. We conclude that this mechanism may have formed Dactyl in the last ≈10% of Ida's lifetime, either after an energetic cratering impact or (more probably) after a collision which shattered Ida without dispersing most of its fragments “to infinity.”

The spin of cosmic dust: rotational bursting of circumsolar dust in the F corona

This paper will list, investigate, and evaluate the various spin mechanisms for cosmic dust particles that have been suggested in the literature. This evaluation will concentrate on the possibility of particle fragmentation (rotational bursting) of cosmic dust. The importance of particle fragmentation is manifested by the fact that dust particle size distribution will be changed. More importantly, repeated fragmentation of interplanetary dust particles will give rise to some of the observed “β meteoroids.” Some of these particles are driven out of the solar system and into interstellar space by solar radiation pressure. If this mass loss mechanism is taking place in stellar systems, then it becomes a source for interstellar dust. This paper also addresses the possibility that massive rotational bursting by circumsolar dust particles is taking place in the F corona region. This rotational bursting of F coronal dust could be taking place because of the classical “Paddack effect,” along with a similar spin mechanism suggested by the author, and caused by coronal mass ejections.

The striated dust tail of Comet West 1976 VI as a particle fragmentation phenomenon

The motions of 16 striae in the dust tail of Comet West are studied. It is found that all 16 striae have originated from particle ejections, and that the particles responsible for the formation of a discrete striae must be emitted simultaneously, be subjected to the same repulsive acceleration in the tail, and break up simultaneously. A strong correlation is found between the ejection times and the times of known explosive events. The repulsive accelerations of particle fragments in the striae vary from 0.6 to 2.7 times the solar attraction, indicating submicron grains of strongly absorbing materials. The repulsive acceleration of parent particles range from 0.55 to 1.10, which is only slightly smaller than those of their fragments and suggests highly nonspherical shapes of parents. The mass of dust in an average striae is estimated to be one-billion grams. Rotational bursting is discussed as a possible fragmentation mechanism. The absence of measurable effects of the Lorentz force indicate an upper limit of a few volts for the electric charge of the fragments.

On the rotational bursting of interplanetary dust particles

A model of the zodiacal cloud is used to evaluate the effects of rotational bursting on interplanetary dust particles caused by the interaction of solar radiation pressure with the irregular surface geometry of the particles. The effectiveness of this mechanism is evaluated using several values for the effective moment arm and tensile strength of the particles. Due to repeated bursting, it is shown that particles spiraling in from the asteroid belt by the Poynting‐Robertson effect do not penetrate inside 1.2 A.U. Spin rate stabilization under the effect of magnetic damping is found to depend critically on the initial heliocentric distance of the particle and on its radius.

5.7 Rotational Bursting of Interplanetary Dust Particles

AbstractSolar radiation pressure can cause rotational bursting and eventual elimination from the solar system of small asymmetric interplanetary particles by a windmill effect. The life span determined by this process for stony meteoritic material or tektite glass with radii of 1 cm is on the order of 105 years. Same size material which contains iron, nickel or aluminum, with properties such that it is subject to 5 percent of the amount of spin damping as pure metals, can be removed from the solar system on the order of 106 years by this process. Ordinary chondritic material, despite its high resistivity, is subject to a type of magnetic spin damping, in addition to the normal spin damping, with the consequent result that this type material cannot be removed from the solar system by this process. This depletion mechanism appears to work faster than the traditional Poynting-Robertson effect by approximately two orders of magnitude for the nonmetallic particles and one order of magnitude for the metallic particles.

5.3 Modeling of the Orbital Evolution of Vaporizing Dust Particles Near the Sun

AbstractThe Poynting-Robertson (P-R) effect (Robertson, 1937, Wyatt and Whipple, 1950), assisted by a pseudo P-R effect due to the sputtering (Whipple, 1955, 1967), is known to cause small dust particles in interplanetary space to spiral toward the sun. Evaporation from the surface of such particles thus increases progressively with time and their size is being reduced accordingly. When the rate of evaporation is no longer negligibly low, it induces on the particle a measurable dynamical effect, which is associated with the implied variations in the magnitude of solar radiation pressure relative to solar attraction. By gradually reducing solar attraction, the particle evaporation tends to increase the orbit dimensions, thus acting against P-R. The P-R inward spiraling, far exceeding the dynamical effect from evaporation at larger heliocentric distances, slows gradually down as the particle approaches the sun, and virtually ceases when the critical distance is reached, where the two forces approximately balance each other. Then, typically, the perihelion distance stabilizes, while the eccentricity starts increasing very rapidly until the particle is swept out of the solar system. This, in brief, is the orbital evolution of a vaporizing particle in the absence of other potentially important but rather poorly known processes, such as particle collisions, rotational bursting, electric charging and interactions with the solar wind and with the interplanetary magnetic field.

Rotational bursting of interplanetary dust particles

Solar radiation pressure can cause rotational bursting and eventual elimination from the solar system of asymmetric dust particles by a windmill effect. The life span against this process for metallic particles with radii of 10−5 to 10−2 cm ranges from 10 to 10,000 years. The effects of magnetic spin damping have been considered in this estimate. This depletion mechanism works faster than the traditional Poynting‐Robertson effect by approximately one order of magnitude for metallic particles and about two orders of magnitude for nonmetallic particles.

Solar radiation induced rotational bursting of interplanetary particles

It is suggested that the magnitudes of the two radiation induced rotational bursting mechanisms have been overestimated and that they do not work significantly faster than the Poynting‐Robertson effect in removal of interplanetary particles.

The microtektite data: Implications for the hypothesis of the lunar origin of tektites

The distribution, of microtektites provides more definite boundaries for the Australasian strewn field. It is found that this field does not encompass the earth. It encompasses so much of the earth, however, that, if it is the result of terrestrial impact, the initial velocity must have been more than 6 km/sec for much of the material and almost none could have reached 7 km/sec. No trace is found of accompanying unmelted soil particles. The microtektites probably cannot be ablation droplets from larger tektites because there are too many and they do not resemble australite flange material; the bottle-green microtektites cannot be explained by processes of volatilization; and there is evidence that, in fact, the Muong Nong tektites are the result of the welding of microtektites. It follows that the microtektites must come directly from the moon, as postulated by Chapman, if they are extraterrestrial at all; the parent-body hypothesis will not work. Presumably tektites which miss the earth on the first encounter are destroyed by the Radzievsky-Paddack effect (rotational bursting induced by asymmetric radiation pressure). The chemical constitution is not decisively different from that indicated by the analyses of Turkevich except in calcium; this can perhaps be explained. Microtektites may represent the unwelded component of a lunar ash flow, of which the Muong Nong tektites are the welded component.

Rotational bursting of small celestial bodies: Effects of radiation pressure

Solar radiation pressure can cause rotational bursting and eventual elimination from the solar system of small nonmagnetic bodies in space by a sort of windmill effect. A time to bursting of about sixty years was calculated for an idealized body. On the basis of a simple experiment, it is estimated that actual bodies, such as nonmagnetic meteorites and tektites, will reach bursting speed in about 60,000 years.