scholarly journals 46. Origins of meteoritic material

1968 ◽  
Vol 33 ◽  
pp. 481-484
Author(s):  
F. L. Whipple
Keyword(s):  
Solar Wind ◽  
Total Mass ◽  
Basic Material ◽  
The Sun ◽  
Input Rate ◽  
Zodiacal Cloud ◽  
The Earth ◽  
Mean Lifetime ◽  
The Mean ◽  
Cometary Origin

The basic material of this discussion is being published under the title ‘On Maintaining the Meteoritic Complex’.* The assumed meteoritic influx on the Earth is derived from measurements of penetration of space vehicles, radio and photographic meteors, meteorite falls, Apollo asteroids, lunar craters, and comets (see Figure 1). I assume that the much higher impact rates from acoustic measures of dust and from collections do not measure the true influx rate. The total flux is some 2 × 10−16 g cm−2 sec−1 on the surface of a corresponding non-gravitating sphere. I take the equivalent space density of some 2 × 10−22 gm cm−3 as applicable over a volume of some 3·5 AU radius about the Sun and i<20° of the ecliptic, giving a total mass of 4·5 × 1019 gm for particles of mass < 102gm. For Earth-crossing orbits the total mass is some 1·3 × 1019 gm. I adopt 2·5 × 1019 gm for the total mass.All known dissipating or destructive factors are included in determining the ‘ecology’ of the meteoritic material. Direct light pressure quickly eliminates particles of the order of 1μ or less in dimension while the solar wind drives away all gases. The Poynting-Robertson effect (PR-effect) is effectively increased by some 22% because of the pseudo PR-effect of the solar wind. Direct sublimation of earthy solids is significant only near the Sun while sputtering losses produced by the solar wind are real but effectively small (~ 10%) compared to spiralling rates by the PR-effect. Magnetic-field, charge and rotation effects may quite possibly be significant but are not yet subject to precise calculations.Space erosion has been demonstrated for stony meteorites and cometary meteoroids (see Table 1). A totally destructive collision is assumed to occur when a particle of mass m is struck by another with mass ≥m/3200. Gravitational elimination effects for the Earth and Venus (time ~ 108 yr), Mars (time ~ 6 × 109 yr) and Jupiter (time ~ 106 yr) are, following öpik, assumed to be negligible for the small Zodiacal Cloud particles, compared to the dissipative effects included above.The mean lifetimes for small particles of mass m are calculated crudely and presented in Table 2 along with the assumed distribution function in mass. The corrected (factor 1/1·3) PR-lifetime is indicated by τPR, erosion by particles of mass < m/3200 by τe, collisional destruction by particles of mass ≥ m/3200 by τc, and the mean lifetime including all these effects by τ.The mean lifetime is much less dependent on mass than might be expected. Averaging all the particles according to mass distribution and τ, the weighted mean lifetime for all material of m< 102gm comes out 8 × 104 yr. Combining this mean lifetime with a total mass of 2·5 × 1019 gm, the average total-input rate to maintain the Zodiacal Cloud in quasi-equilibrium becomes some 10 tons sec−1. Note that this input rate may be considerably overestimated because I have not included the contributions to the cloud by broken fragments.It appears quite possible that comets can supply the needed 10 tons sec−1 injected into orbits totally within that of Jupiter. Fragile carbonaceous chondrites and ‘half-baked asteroids’ (see Appendix), however, may compete with comets in contributing to the fireballs and possibly to the visual meteors. The stony meteorites may be maintained by collisional spallation from Earth-crossing asteroids induced by smaller bodies, the Apollo asteroids being derived from the asteroid belt by the gravitational effects of Mars. The data and theory are not yet adequate to provide a definitive solution to the problem of asteroidal vs. cometary origin for the Apollo asteroids.One asks whether McCrosky's fireballs might have originated directly from comets, not primarily from Apollo asteroids. Jupiter crossings (τ ~ 106 yr) might have eliminated most of the orbits with aphelia beyond Jupiter's. A rough calculation failed by a factor of 3–5 in accounting for the reduction in numbers of orbits with large aphelion distances among McCrosky's fireballs as compared to the number among photographic meteors. This leaves the question essentially unsolved but also allows the possibility that a considerable fraction of McCrosky's fireballs may be of direct cometary origin, in typical short-period comet orbits, rather than Apollo-asteroid fragments.

scholarly journals A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Kazuo Shiokawa ◽  
Katya Georgieva
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Solar Wind Plasma ◽  
The Sun ◽  
Scientific Program ◽  
Solar Cycles ◽  
Grand Minimum ◽  
The Earth ◽  
Earth Connection ◽  
Near Future

AbstractThe Sun is a variable active-dynamo star, emitting radiation in all wavelengths and solar-wind plasma to the interplanetary space. The Earth is immersed in this radiation and solar wind, showing various responses in geospace and atmosphere. This Sun–Earth connection variates in time scales from milli-seconds to millennia and beyond. The solar activity, which has a ~11-year periodicity, is gradually declining in recent three solar cycles, suggesting a possibility of a grand minimum in near future. VarSITI—variability of the Sun and its terrestrial impact—was the 5-year program of the scientific committee on solar-terrestrial physics (SCOSTEP) in 2014–2018, focusing on this variability of the Sun and its consequences on the Earth. This paper reviews some background of SCOSTEP and its past programs, achievements of the 5-year VarSITI program, and remaining outstanding questions after VarSITI.

3D MHD study of the Earth magnetosphere response during extreme space weather conditions

2021 ◽  
Author(s):  
Jacobo Varela Rodriguez ◽  
Sacha A. Brun ◽  
Antoine Strugarek ◽  
Victor Réville ◽  
Filippo Pantellini ◽  
...  
Keyword(s):  
Solar Wind ◽  
Space Weather ◽  
Coronal Mass Ejections ◽  
Main Sequence ◽  
Dynamic Pressure ◽  
Weather Conditions ◽  
The Sun ◽  
Earth Surface ◽  
The Earth ◽  
The Imf

&lt;p&gt;&lt;span&gt;The aim of the study is to analyze the response of the Earth magnetosphere for various space weather conditions and model the effect of interplanetary coronal mass ejections. The magnetopause stand off distance, open-closed field lines boundary and plasma flows towards the planet surface are investigated. We use the MHD code PLUTO in spherical coordinates to perform a parametric study regarding the dynamic pressure and temperature of the solar wind as well as the interplanetary magnetic field intensity and orientation. The range of the parameters analyzed extends from regular to extreme space weather conditions consistent with coronal mass ejections at the Earth orbit. The direct precipitation of the solar wind on the Earth day side at equatorial latitudes is extremely unlikely even during super coronal mass ejections. For example, the SW precipitation towards the Earth surface for a IMF purely oriented in the Southward direction requires a IMF intensity around 1000 nT and the SW dynamic pressure above 350 nPa, space weather conditions well above super-ICMEs. The analysis is extended to previous stages of the solar evolution considering the rotation tracks from Carolan (2019). The simulations performed indicate an efficient shielding of the Earth surface 1100 Myr after the Sun enters in the main sequence. On the other hand, for early evolution phases along the Sun main sequence once the Sun rotation rate was at least 5 times faster (&lt; 440 Myr), the Earth surface was directly exposed to the solar wind during coronal mass ejections (assuming today&amp;#180;s Earth magnetic field). Regarding the satellites orbiting the Earth, Southward and Ecliptic IMF orientations are particularly adverse for Geosynchronous satellites, partially exposed to the SW if the SW dynamic pressure is 8-14 nPa and the IMF intensity 10 nT. On the other hand, Medium orbit satellites at 20000 km are directly exposed to the SW during Common ICME if the IMF orientation is Southward and during Strong ICME if the IMF orientation is Earth-Sun or Ecliptic. The same way, Medium orbit satellites at 10000 km are directly exposed to the SW if a Super ICME with Southward IMF orientation impacts the Earth.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;This work was supported by the project 2019-T1/AMB-13648 founded by the Comunidad de Madrid, grants ERC WholeSun, Exoplanets A and PNP. We extend our thanks to CNES for Solar Orbiter, PLATO and Meteo Space science support and to INSU/PNST for their financial support.&lt;/p&gt;

On an inequality of long period in the motions of the Earth and Venus

1837 ◽  
Vol 3 ◽  
pp. 77-78
Keyword(s):  
Principal Term ◽  
The Sun ◽  
Method Of Calculation ◽  
The Third ◽  
Long Period ◽  
Mean Motion ◽  
The Earth ◽  
The Mean ◽  
The Difference

The author had pointed out, in a paper published in the Philosophical Transactions for 1828, on the corrections of the elements of Delambre’s Solar Tables, that the comparison of the corrections of the epochs of the sun and the sun’s perigee, given by the late observations, with the corrections given by the observations of the last century, appears to indicate the existence of some inequality not included in the arguments of those tables. As it was necessary, therefore, to seek for some inequality of long period, he commenced an examination of the mean motions of the planets, with the view of discovering one whose ratio to the mean motion of the earth could be expressed very nearly by a proportion of which the terms are small. The appearances of Venus are found to recur in very nearly the same order every eight years; some multiple, therefore, of the periodic time of Venus is nearly equal to eight years. It is easily seen that this multiple must be thirteen; and consequently eight times the mean motion of Venus is nearly equal to thirteen times the mean motion of the earth. The difference is about one 240th of the mean annual motion of the earth; and it implies the existence of an inequality of which the period is about 240 years. No term has yet been calculated whose period is so long with respect to the periodic time of the planets disturbed. The value of the principal term, calculated from the theory, was given by the author in a postscript to the paper above referred to. In the present memoir he gives an account of the method of calculation, and includes also other terms which are necessarily connected with the principal inequality. The first part treats of the perturbation of the earth’s longitude and radius victor; the second of the perturbation of the earth in latitude; and the third of the perturbations of Venus depending upon the same arguments.

scholarly journals On the Causes of Palaeoclimatic Variations and of the Ice Ages in Particular

1953 ◽  
Vol 2 (13) ◽  
pp. 213-218
Author(s):  
E. J. Öpik
Keyword(s):  
Nuclear Reactions ◽  
Gas Diffusion ◽  
Seasonal Temperature ◽  
The Sun ◽  
Orbital Elements ◽  
Ice Ages ◽  
Solar Mass ◽  
The Earth ◽  
Change In The Mean ◽  
The Mean

AbstractA method of quantitative climatological analysis is developed by applying the principle of geometric similarity to the convective heat transport, which is assumed to vary with the 1.5 power of temperature difference. The method makes possible the calculation of the change in the mean annual, or seasonal temperature, produced by a variation in insolation, cloudiness, snow cover, etc.It is shown that the variations in the orbital elements of the earth cannot account for the phenomena of the ice ages; the chronology of the Quaternary, based on these variations, has no real foundation.Palaeoclimatic variations are most probably due to variations of solar luminosity. These can be traced to periodical re-adjustments in the interior of the sun, produced by an interplay between nuclear reactions and gas diffusion, repeating themselves after some 250 million years. Complications from the outer envelope of the sun lead to additional fluctuations of a shorter period, of the order of 100,000 years to be identified with the periodical advance and retreat of the glaciers during the Quaternary.Calculations of the variations of luminosity in a star of solar mass substantiate this hypothesis.

On the Drag parameter of ICME propagation models

2020 ◽  
Author(s):  
Gianluca Napoletano ◽  
Raffaello Foldes ◽  
Dario Del Moro ◽  
Francesco Berrilli ◽  
Luca Giovannelli ◽  
...  
Keyword(s):  
Solar Wind ◽  
Travel Time ◽  
Initial Conditions ◽  
Solar Wind Speed ◽  
Distribution Functions ◽  
Model Parameters ◽  
Wind Condition ◽  
The Sun ◽  
The Earth ◽  
External Fluid

&lt;p&gt;ICME (Interplanetary Coronal Mass Ejection) are violent phenomena of solar activity that affect the whole heliosphere and the prediction of their impact on different solar system bodies is one of the primary goals of the planetary space weather forecasting. The travel time of an ICME from the Sun to the Earth can be computed through the Drag-Based Model (DBM), which is based on a simple equation of motion for the ICME defining its acceleration as a=-&amp;#915;(v-w)v-w, where a and v are the CME acceleration and speed, w is the ambient solar-wind speed and &amp;#915; is the so-called drag parameter (Vrs&amp;#780;nak et al., 2013).&lt;br&gt;In this framework, &amp;#915; depends on the ICME mass and cross-section, on the solar-wind density and, to a lesser degree, on other parameters. The typical working hypothesis for DBM implies that both &amp;#915; and w are constant far from the Sun. To run the codes, forecasters use empirical&lt;br&gt;input values for &amp;#915; and w, derived by pre-existent knowledge of solar-wind condition and by solving the &amp;#8220;inverted problem&amp;#8221; (where the ICME travel time is known and the unknowns are &amp;#915; and/or w). In&lt;br&gt;the 'Ensemble' approaches (Dumbovich et al., 2018; Napoletano et al. 2018), the uncertainty about the actual values of such inputs are rendered by Probability Distribution Functions (PDFs), accounting for the values variability and our lack of knowledge. Among those PDFs, that of &amp;#915; is poorly defined due to the relatively scarce statistics of recorded values.&amp;#160;&lt;/p&gt;&lt;p&gt;Employing a list of past ICME events, for which initial conditions when leaving the Sun and arrival conditions at the Earth are known, we employ a statistical approach to the Drag-Based Model to determine a measure of &amp;#915; and w for each case. This allows to obtain distributions for the model parameters on experimental basis and, more importantly, to test whether different conditions of relative velocity to the solar wind influence the value of the drag efficiency, as it must be expected for solid objects moving into an external fluid. In addition, we perform numerical simulations of a solid ICME-shaped structure moving into the solar-wind modelled as an external fluid. Outcomes from these simulations are compared with our experimental results, and thus employed to interpret them on physical basis.&lt;/p&gt;

scholarly journals I. An account of the Sun's distance from the Earth, deduced from Mr. Short's observations relating to the horizontal parallax of the Sun: In a letter from Peter Daval, Esq; V. P. of R. S. to James Barrow, Esq; V. P. of R. S

1763 ◽  
Vol 53 ◽  
pp. 1-2
Keyword(s):  
The Sun ◽  
The Earth ◽  
The Mean

According to Mr. Short, the mean horizontal parallax of the Sun is 8", 65. Now this parallax is the angle, which the semidiameter of the earth subtends, being seen from the Sun.

scholarly journals Observations of interplanetary scintillation in China

2012 ◽  
Vol 8 (S294) ◽  
pp. 487-488
Author(s):  
Li-Jia Liu ◽  
Bo Peng
Keyword(s):  
Solar Wind ◽  
Interplanetary Medium ◽  
Interplanetary Space ◽  
Solar Wind Speed ◽  
Small Diameter ◽  
Primary Source ◽  
Radio Sources ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
The Earth

AbstractThe Sun affects the Earth in multiple ways. In particular, the material in interplanetary space comes from coronal expansion in the form of solar wind, which is the primary source of the interplanetary medium. Ground-based Interplanetary Scintillation (IPS) observations are an important and effective method for measuring solar wind speed and the structures of small diameter radio sources. In this paper we will discuss the IPS observations in China.

scholarly journals On a method of comparing the light of the Sun with that of the fixed stars

1833 ◽  
Vol 2 ◽  
pp. 355-355
Keyword(s):  
Full Moon ◽  
Angular Distance ◽  
The Other ◽  
The Sun ◽  
Proper Distance ◽  
The Earth ◽  
Direct Light ◽  
Glass Bulb ◽  
The Mean ◽  
Made In

In the Philosophical Transactions for the year 1767, a suggestion is thrown out by Mr. Michell, that a comparison between the light received from the sun and any of the fixed stars, might furnish data for estimating their relative distances; but no such direct comparison had been attempted. Dr. Wollaston was led to infer from some observations that he made in the year 1799, that the direct light of the sun is about one million times more intense than that of the full moon, and therefore very many million times greater than that of all the fixed stars taken collectively. In order to compare the light of the sun with that of a star, he took, as an intermediate object of comparison, the light of a candle reflected from a small bulb, about a quarter of an inch in diameter, filled with quicksilver, and seen, by one eye, through a lens of two inches focus, at the same time that the star or the sun’s image, placed at a proper distance, was viewed by the other eye through a telescope. The mean of various trials seemed to show that the light of Sirius is equal to that of the sun seen in a glass bulb one tenth of an inch in diameter, at the distance of 210 feet, or that they are in the proportion of one to ten thousand millions; but as nearly one half of the light is lost by reflection, the real proportion between the light from Sirius and the sun is not greater than that of one to twenty thousand millions. If the annual parallax of Sirius be half a second, corresponding to a distance of 525,481 times that of the sun from the earth, its diameter would be 3⋅7 times that of the sun, and its light 13⋅8 times as great. The distance at which the sun would require to be viewed, so that its brightness might be only equal to that of Sirius, would be 141,421 times its present distance; and if still in the ecliptic, its annual parallax in longitude would be nearly 3″; but if situated at the same angular distance from the ecliptic as Sirius is, it would have an annual parallax, in latitude, of 1″⋅8.

scholarly journals Domains of Magnetic Pressure Balance in Parker Solar Probe Observations of the Solar Wind

2021 ◽  
Vol 923 (2) ◽  
pp. 158
Author(s):  
David Ruffolo ◽  
Nawin Ngampoopun ◽  
Yash R. Bhora ◽  
Panisara Thepthong ◽  
Peera Pongkitiwanichakul ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Density Fluctuations ◽  
Magnetic Pressure ◽  
Inverse Association ◽  
The Sun ◽  
Thin Domains ◽  
Pressure Balance ◽  
Filling Fraction ◽  
The Mean

Abstract The Parker Solar Probe (PSP) spacecraft is performing the first in situ exploration of the solar wind within 0.2 au of the Sun. Initial observations confirmed the Alfvénic nature of aligned fluctuations of the magnetic field B and velocity V in solar wind plasma close to the Sun, in domains of nearly constant magnetic field magnitude ∣ B ∣, i.e., approximate magnetic pressure balance. Such domains are interrupted by particularly strong fluctuations, including but not limited to radial field (polarity) reversals, known as switchbacks. It has been proposed that nonlinear Kelvin–Helmholtz instabilities form near magnetic boundaries in the nascent solar wind leading to extensive shear-driven dynamics, strong turbulent fluctuations including switchbacks, and mixing layers that involve domains of approximate magnetic pressure balance. In this work we identify and analyze various aspects of such domains using data from the first five PSP solar encounters. The filling fraction of domains, a measure of Alfvénicity, varies from median values of 90% within 0.2 au to 38% outside 0.9 au, with strong fluctuations. We find an inverse association between the mean domain duration and plasma β. We examine whether the mean domain duration is also related to the crossing time of spatial structures frozen into the solar wind flow for extreme cases of the aspect ratio. Our results are inconsistent with long, thin domains aligned along the radial or Parker spiral direction, and compatible with isotropic domains, which is consistent with prior observations of isotropic density fluctuations or flocculae in the solar wind.

scholarly journals Magnetospheric response to the interaction with the sporadic solar wind diamagnetic structure

2021 ◽  
Vol 7 (3) ◽  
pp. 11-28
Author(s):  
Vladimir Parkhomov ◽  
Viktor Eselevich ◽  
Maxim Eselevich ◽  
Alexei Dmitriev ◽  
Alla Suvorova ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Classical Model ◽  
Ion Concentration ◽  
The Sun ◽  
Large Size ◽  
The Earth ◽  
Night Side ◽  
Mass Ejection ◽  
Deep Modulation

We report the results of a study on the movement of the solar wind diamagnetic structure (DS), which is a sequence of smaller-scale microDS being part of the May 18, 2013 coronal mass ejection, from a source on the Sun to Earth’s surface. DS determined from the high negative correlation coefficient (r=–0.9) between the IMF modulus (B) and the SW density (N) on the ACE and Wind satellites at the L1 point, on the THB and THC satellites (r=–0.9) in near-Earth orbit, and on the THA satellite inside the magnetosphere is carried by the solar wind from the Sun to Earth’s orbit, while maintaining its fine internal structure. Having a large size in the radial direction (≈763 Rᴇ, where Rᴇ is the Earth radius), DS flows around the magnetosphere. At the same time, microDS of size ≤13 Rᴇ passes through the bow shock and magnetopause as a magnetized plasmoid in which the ion concentration increases from 10 cm⁻³ to 90 cm⁻³, and the velocity decreases as it moves toward the magnetotail. When a microDS passes through the magnetopause, a pulsed electric field of ~400 mV/m is generated with subsequent oscillations with a period of T~200 s and an amplitude of ~50 mV/m. The electric field accelerates charged particles of the radiation belt and produces modulated fluxes of protons in an energy range 95–575 keV on the day side and electrons in 40–475 keV and protons in 95–575 keV on the night side. In the duskside magnetosphere (19–23 MLT), the substorm activation is observed in geomagnetic pulsations and auroras, but without a magnetic negative bay. In the post-midnight sector (01–05 MLT), a sawtooth substorm occurs without the growth phase and breakup with deep modulation of the ionospheric current and auroral absorption. The duration of all phenomena in the magnetosphere and on Earth is determined by the period of interaction between DS and the magnetosphere (~4 hrs). To interpret the regularities of the magnetospheric response to the interaction with DS, we consider alternative models of the impulsive passage of DS from SW to the magnetosphere and the classical model of reconnection of IMF and the geomagnetic field.

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