Mechanisms and Evolution of Geoeffective Large-Scale Plasma Jets in the Magnetosheath

Geoeffective magnetosheath plasma jets (those that interact with the magnetopause) are an important area of research and technology, since they affect the “space-weather” around the Earth. We identified such large-scale magnetosheath plasma jets with a duration of >30 s using plasma and magnetic data acquired from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) multi-spacecraft experiment during the years 2007 to 2009. We present a statistical survey of 554 of such geoeffective jets and elaborate on four mechanisms for the generation of these jets as the upstream solar wind structures of tangential discontinuities (TDs), rotational discontinuities (RDs), the quasi-radial interplanetary magnetic field (rIMF) and the collapsing foreshock (CFS) interrupting the rIMF intervals. We found that 69% of the jets are generated due to the interaction between interplanetary discontinuities (TD: 24%, RD: 25%, CFS: 20%) with the bow shock. Slow and weak jets due to the rIMF contributed to 31% of these jets. The CFS and rIMF were found to be similar in their characteristics. TDs and RDs contributed to most of the fast and powerful jets, with large spatial scales, which might be attributed to transient effects in the travelling foreshock.

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Enhanced dissipation for quasi-geostrophic motion over small-scale topography

Journal of Fluid Mechanics ◽

10.1017/s0022112099007430 ◽

2000 ◽

Vol 407 ◽

pp. 105-122 ◽

Cited By ~ 9

Author(s):

JACQUES VANNESTE

Keyword(s):

Large Scale ◽

Spatial Scales ◽

Additional Term ◽

Equation Of Motion ◽

Small Scale ◽

Two Dimensional ◽

Turbulent Dissipation ◽

Dissipative Term ◽

History Of ◽

Large Scale Flow

The effect of a small-scale topography on large-scale, small-amplitude oceanic motion is analysed using a two-dimensional quasi-geostrophic model that includes free-surface and β effects, Ekman friction and viscous (or turbulent) dissipation. The topography is two-dimensional and periodic; its slope is assumed to be much larger than the ratio of the ocean depth to the Earth's radius. An averaged equation of motion is derived for flows with spatial scales that are much larger than the scale of the topography and either (i) much larger than or (ii) comparable to the radius of deformation. Compared to the standard quasi-geostrophic equation, this averaged equation contains an additional dissipative term that results from the interaction between topography and dissipation. In case (i) this term simply represents an additional Ekman friction, whereas in case (ii) it is given by an integral over the history of the large-scale flow. The properties of the additional term are studied in detail. For case (i) in particular, numerical calculations are employed to analyse the dependence of the additional Ekman friction on the structure of the topography and on the strength of the original dissipation mechanisms.

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A plasma flow vortex in the magnetotail and its related ionospheric signatures

Annales Geophysicae ◽

10.5194/angeo-30-537-2012 ◽

2012 ◽

Vol 30 (3) ◽

pp. 537-544 ◽

Cited By ~ 5

Author(s):

C. L. Tang

Keyword(s):

Plasma Flow ◽

Plasma Sheet ◽

Large Scale ◽

Time History ◽

High Energy ◽

Auroral Oval ◽

Fort Smith ◽

Flow Speeds ◽

History Of ◽

Flow Vortex

Abstract. We presented a large-scale plasma flow vortex event that occurred on 1 March 2009 observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. During the interval, THEMIS satellites were located in the premidnight region between 11 and 16 RE downtail. Dawnward-earthward plasma flows were seen initially in the magnetotail, followed by duskward-tailward flows. This suggests that a clockwise plasma flow vortex (seen from above the equatorial plane) was observed on the dawn side of the plasma sheet. Furthermore, high energy (>1 keV) electrons were observed. Auroral images at 427.8 nm and THEMIS white light all-sky imager (ASI) at Fort Smith showed a discrete auroral patch formed at the poleward of the auroral oval, it then intensified. It extended eastward and equatorward first and followed by westward motion to form the clockwise auroral vortex. The auroral feature corresponded to the ionospheric signatures of the plasma flow vortex in the magnetotail when the Alfvén transit time between the magnetotail and the ionosphere was taken into account. We suggest that the large-scale clockwise plasma flow vortex in association with the high energy (>1 keV) electrons on the dawn side of the plasma sheet generated a downward field-aligned current (FAC) that caused the related ionospheric signatures. The plasma flow vortex had rotational flow speeds of up to 300 km s−1. The current density associated with the plasma flow vortex was estimated at 2.0 μA m−2, mapped to the ionosphere.

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Jets in the Magnetosheath: IMF Control of Where They Occur

10.5194/angeo-2019-65 ◽

2019 ◽

Author(s):

Laura Vuorinen ◽

Heli Hietala ◽

Ferdinand Plaschke

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Spatial Distribution ◽

Interplanetary Magnetic Field ◽

Cone Angle ◽

Time History ◽

Bow Shock ◽

The Earth ◽

Parallel Side ◽

History Of

Abstract. Magnetosheath jets are localized regions of plasma that move faster towards the Earth than the surrounding magnetosheath plasma. Due to their high velocities, they can cause indentations when colliding into the magnetopause and trigger processes such as magnetic reconnection and magnetopause surface waves. We statistically study the occurrence of these jets in the subsolar magnetosheath using measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and OMNI solar wind data from 2008–2011. We present the observations in the BIMF-vSW plane and study the spatial distribution of jets during different interplanetary magnetic field (IMF) orientations. Jets occur downstream of the quasi-parallel bow shock approximately 9 times as often as downstream of the quasi-perpendicular shock, suggesting that foreshock processes are responsible for most jets. For oblique IMF, with 30°–60° cone angle, the occurrence increases monotonically from the quasi-perpendicular side to the quasi-parallel side. This study offers predictability for the numbers and locations of jets observed during different IMF orientations allowing us to better forecast the formation of these jets and their impact on the magnetosphere.

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The early evolution of the earth, the beginning of its geological history: how and when the granitoid magmas appeared

LITOSFERA ◽

10.24930/1681-9004-2018-18-5-653-671 ◽

2018 ◽

pp. 653-671 ◽

Cited By ~ 1

Author(s):

Mikhail I. Kuzmin ◽

Vladimir V. Yarmolyuk ◽

Alexander B. Kotov

Keyword(s):

Large Scale ◽

Mantle Plumes ◽

Geological History ◽

Leading Role ◽

The Earth ◽

Geological Situation ◽

History Of ◽

Archean Crust ◽

Primary Substance ◽

Basaltic Crust

The Earth has a number of differences from the planets of the Solar System and other star-planetary systems. These differences were acquired during its formation and geological history. In the early Chaotic eon occurred the accretion of the Earth, the separation of the primary substance of the Earth into a mantle and a nucleus, a satellite of the Earth - the Moon appeared. 4500 Ma ago in the Gadey aeon the geological history of the Earth began. At this time, the endogenous processes on the Earth were controlled to a great extent by meteorite-asteroid bombardments, which caused large-scale melting and differentiation of the upper shells of the Earth. In the magmatic chambers differentiation proceeded until the appearance of melts of granitoid composition. The continental crust of Gadey time was almost completely destroyed by meteoric bombardments, the last heavy bombardment occurred at the end of the Gadey aeon 4000-3900 Ma ago. The geological situation of the Gadey time can be judged only from the preserved zircons from the rocks of that epoch. In particular, their geochemical features indicate that the Earth has an atmosphere. The Gadey eon was replaced by the Archean one, from which the processes of self-organization began to predominate on the Earth. At this time, a crust composed of komatiite-basalt and tonalite-trondhjemite-granodiorite (TTG) series of rocks was formed. In its formation, the processes of sagduction (vertical growth of the crust) over the rising mantle plumes was played the leading role. At the same time the lower basaltic crust was bured in the mantle, eclogitized and melted, which led to the appearance of the sodium series of TTG rocks. At the end of the Archean 3.1-3.0 Ga tectonics of the cover (LID tectonics), which determined the style of the structure and development of the Archean crust, is replaced by the tectonics of small plates, which was later replaced by modern tectonics - the tectonics of plates combined with mantle plumes.

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Dynamical features of the near-Hermean environment under different solar wind conditions

10.5194/egusphere-egu21-8215 ◽

2021 ◽

Author(s):

Anna Milillo ◽

Tommaso Alberti ◽

Stavro L. Ivanovski ◽

Monica Laurenza ◽

Stefano Massetti ◽

...

Keyword(s):

Solar Wind ◽

Large Scale ◽

Spatial Scales ◽

Local Source ◽

Hilbert Huang Transform ◽

Ulf Wave ◽

Large Scale Field ◽

Upstream Solar Wind ◽

Global And Local ◽

Planetary Magnetic Field

<p>The interaction between the interplanetary medium and planetary environments gives rise to different phenomena on several temporal and spatial scales. Here we use the Hilbert-Huang Transform (HHT) to characterize both local and global properties of Mercury's environment as seen during two MESSENGER flybys with different upstream solar wind conditions. Hence, we may infer that the near-Mercury environment presents some different local features with respect to the ambient solar wind, due to both interaction processes and intrinsic structures of the Hermean environment. Our findings support the ion kinetic nature of the Hermean plasma structures, with the magnetosheath being characterized by inhomogeneous ion-kinetic intermittent fluctuations, superimposed to both MHD fluctuations and large-scale field structure. We show that the HHT analysis allow to capture and reproduce some interesting features of the Hermean environment as flux transfer events, Kelvin-Helmholtz vortices, and ULF wave activity, thus providing a suitable method for characterizing physical processes of different nature. Our approach demonstrate to be very promising for the characterization of the structure and dynamics of planetary magnetic field at different scales, for the identification of boundaries, and for discriminating the different scale-dependent features of global and local source processes that can be used for modelling purposes.</p>

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Jets in the magnetosheath: IMF control of where they occur

Annales Geophysicae ◽

10.5194/angeo-37-689-2019 ◽

2019 ◽

Vol 37 (4) ◽

pp. 689-697 ◽

Cited By ~ 6

Author(s):

Laura Vuorinen ◽

Heli Hietala ◽

Ferdinand Plaschke

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Spatial Distribution ◽

Interplanetary Magnetic Field ◽

Cone Angle ◽

Time History ◽

Bow Shock ◽

The Earth ◽

Parallel Side ◽

History Of

Abstract. Magnetosheath jets are localized regions of plasma that move faster towards the Earth than the surrounding magnetosheath plasma. Due to their high velocities, they can cause indentations when colliding into the magnetopause and trigger processes such as magnetic reconnection and magnetopause surface waves. We statistically study the occurrence of these jets in the subsolar magnetosheath using measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and OMNI solar wind data from 2008 to 2011. We present the observations in the BIMF–vSW plane and study the spatial distribution of jets during different interplanetary magnetic field (IMF) orientations. Jets occur downstream of the quasi-parallel bow shock approximately 9 times as often as downstream of the quasi-perpendicular shock, suggesting that foreshock processes are responsible for most jets. For an oblique IMF, with 30–60∘ cone angle, the occurrence increases monotonically from the quasi-perpendicular side to the quasi-parallel side. This study offers predictability for the numbers, locations, and magnetopause impact rates of jets observed during different IMF orientations, allowing us to better forecast the formation of these jets and their impact on the magnetosphere.

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Sample Collection and Return from Mars: Optimising Sample Collection Based on the Microbial Ecology of Terrestrial Volcanic Environments

Space Science Reviews ◽

10.1007/s11214-019-0609-7 ◽

2019 ◽

Vol 215 (7) ◽

Author(s):

Charles S. Cockell ◽

Sean McMahon ◽

Darlene S. S. Lim ◽

John Rummel ◽

Adam Stevens ◽

...

Keyword(s):

Microbial Ecology ◽

Large Scale ◽

Spatial Scales ◽

A Priori ◽

Volcanic Rocks ◽

Hydrothermal Systems ◽

Sample Collection ◽

Heterogeneous Distribution ◽

Microbial Distribution ◽

The Earth

Abstract With no large-scale granitic continental crust, all environments on Mars are fundamentally derived from basaltic sources or, in the case of environments such as ices, evaporitic, and sedimentary deposits, influenced by the composition of the volcanic crust. Therefore, the selection of samples on Mars by robots and humans for investigating habitability or testing for the presence of life should be guided by our understanding of the microbial ecology of volcanic terrains on the Earth. In this paper, we discuss the microbial ecology of volcanic rocks and hydrothermal systems on the Earth. We draw on microbiological investigations of volcanic environments accomplished both by microbiology-focused studies and Mars analog studies such as the NASA BASALT project. A synthesis of these data emphasises a number of common patterns that include: (1) the heterogeneous distribution of biomass and diversity in all studied materials, (2) physical, chemical, and biological factors that can cause heterogeneous microbial biomass and diversity from sub-millimetre scales to kilometre scales, (3) the difficulty of a priori prediction of which organisms will colonise given materials, and (4) the potential for samples that are habitable, but contain no evidence of a biota. From these observations, we suggest an idealised strategy for sample collection. It includes: (1) collection of multiple samples in any given material type (∼9 or more samples), (2) collection of a coherent sample of sufficient size (${\sim}10~\mbox{cm}^{3}$ ∼ 10 cm 3 ) that takes into account observed heterogeneities in microbial distribution in these materials on Earth, and (3) collection of multiple sample suites in the same material across large spatial scales. We suggest that a microbial ecology-driven strategy for investigating the habitability and presence of life on Mars is likely to yield the most promising sample set of the greatest use to the largest number of astrobiologists and planetary scientists.

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Anti-sunward high-speed jets in the subsolar magnetosheath

Annales Geophysicae ◽

10.5194/angeo-31-1877-2013 ◽

2013 ◽

Vol 31 (10) ◽

pp. 1877-1889 ◽

Cited By ~ 56

Author(s):

F. Plaschke ◽

H. Hietala ◽

V. Angelopoulos

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

High Speed ◽

Dynamic Pressure ◽

Time History ◽

Data Set ◽

Wind Variability ◽

History Of ◽

Favorable Conditions ◽

Upstream Solar Wind

Abstract. Using 2008–2011 data from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft in Earth's subsolar magnetosheath, we study high-speed jets identified as intervals when the anti-sunward component of the dynamic pressure in the subsolar magnetosheath exceeds half of its upstream solar wind value. Based on our comprehensive data set of 2859 high-speed jets, we obtain the following statistical results on jet properties and favorable conditions: high-speed jets occur predominantly downstream of the quasi-parallel bow shock, i.e., when interplanetary magnetic field cone angles are low. Apart from that, jet occurrence is only very weakly dependent (if at all) on other upstream conditions or solar wind variability. Typical durations and recurrence times of high-speed jets are on the order of tens of seconds and a few minutes, respectively. Relative to the ambient magnetosheath, high-speed jets exhibit higher speed, density and magnetic field intensity, but lower and more isotropic temperatures. They are almost always super-Alfvénic, often even super-magnetosonic, and typically feature 6.5 times as much dynamic pressure and twice as much total pressure in anti-sunward direction as the surrounding plasma does. Consequently, they are likely to have significant effects on the magnetosphere and ionosphere if they impinge on the magnetopause.

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Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets

Annales Geophysicae ◽

10.1007/s00585-999-1020-6 ◽

1999 ◽

Vol 17 (8) ◽

pp. 1020-1039 ◽

Cited By ~ 15

Author(s):

C. E. Valladares ◽

D. Alcaydé ◽

J. V. Rodriguez ◽

J. M. Ruohoniemi ◽

A. P. Van Eyken

Keyword(s):

Electric Fields ◽

Plasma Density ◽

Large Scale ◽

Frictional Heating ◽

Time History ◽

Plasma Jets ◽

Local Times ◽

Number Density ◽

Ion Temperature ◽

Polar Cap

Abstract. We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two different types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The first event consisted of the passage of traveling convection vortices (TCV). The other event occurred in association with the development of large plasma jets (LPJ) embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also confirmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O+ recombination due to an elevated Ti, which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km) longitudinal extension and were 200-300 km in width. They were seen principally with the Sondrestrom, and SuperDARN radars. Enhanced ion temperature (Ti) was also observed by the Sondrestrom and EISCAT radars. These channels of high Ti were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma flow is important to define the depth of the density depletion. Systematic changes in the latitudinal location and in the intensity of the LPJs were observed in the 2 min time resolution data of the SuperDARN radars. The effect of the abrupt changes in the LPJs location is to create regions containing dayside plasma almost detached from the rest of the oval density. One of these density features was seen by the Sondrestrom radar at 1542 UT. The data presented here suggest that two plasma structuring mechanisms (TCVs and LPJs) can act tens of minutes apart to produce higher levels of density structures in the near noon F-region ionosphere.Key words. Ionosphere (ionospheric irregularities) · Magnetospheric physics (electric fields; polar cap phenomena)

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About the book “History of the Earth. From Stardust to Stardust”

Proceedings of higher educational establishments Geology and Exploration ◽

10.32454/0016-7762-2020-63-2-97-100 ◽

2020 ◽

Vol 63 (2) ◽

pp. 97-100

Author(s):

V. N. Komarov

Keyword(s):

Large Scale ◽

Final Section ◽

Book History ◽

Evolutionary Development ◽

The Earth ◽

Organic World ◽

History Of ◽

Nutritional Strategies ◽

Opening Up ◽

Detailed Picture

The book gives a detailed picture of the Earth’s history. The authors describe successive changes in paleogeographic settings and their underlying reasons, changes in ocean levels and continent outlines, the processes of volcanism and basic laws of mineral formation. Particular attention is paid to the most important arogeneses of evolutionary development, which created conditions for organisms to leave their habitual environment, thus opening up new prospects for a wide ecological expansion. As nodal points in the evolution of individual groups of the organic world and landscape changes, the authors acquaint readers with the skeletal revolution, the emergence of organs of vision, the appearance of roots in plants, the formation of first soils, the emergence of vertebrates on land, the flourishing of insects, the appearance of mammals and flowering plants. Detailed information on the most interesting extinct organisms of certain periods of the Earth’s geological history is given. Their morphology, size, lifestyle, nutritional strategies and causes of extinction are considered. Of particular interest is the part devoted to the appearance and development of mankind, as well as its large-scale comprehensive impact on nature. In the final section of the book, the authors reflect on the future of our planet.

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