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Journal articles on the topic 'Earthwarks'

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Author: Grafiati

Published: 6 September 2023

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1

Machida, S., Y. Miyashita, A. Ieda, M. Nosé, V. Angelopoulos, and J. P. McFadden. "Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data." Annales Geophysicae 32, no. 2 (February 17, 2014): 99–111. http://dx.doi.org/10.5194/angeo-32-99-2014.

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Abstract. To investigate the physical mechanism responsible for substorm triggering, we performed a superposed-epoch analysis using plasma and magnetic-field data from THEMIS probes. Substorm onset timing was determined based on auroral breakups detected by all-sky imagers at the THEMIS ground-based observatories. We found earthward flows associated with north–south auroral streamers during the substorm growth phase. At around X = −12 Earth radii (RE), the northward magnetic field and its elevation angle decreased markedly approximately 4 min before substorm onset. Moreover, a northward magnetic-field increase associated with pre-onset earthward flows was found at around X = −17 RE. This variation indicates that local dipolarization occurs. Interestingly, in the region earthwards of X = −18 RE, earthward flows in the central plasma sheet (CPS) reduced significantly approximately 3 min before substorm onset, which was followed by a weakening of dawn-/duskward plasma-sheet boundary-layer flows (subject to a 1 min time lag). Subsequently, approximately 1 min before substorm onset, earthward flows in the CPS were enhanced again and at the onset, tailward flows started at around X = −20 RE. Following substorm onset, an increase in the northward magnetic field caused by dipolarization was found in the near-Earth region. Synthesizing these results, we confirm our previous results based on GEOTAIL data, which implied that significant variations start earlier than both current disruption and magnetic reconnection, at approximately 4 min before substorm onset roughly halfway between the two regions of interest; i.e. in the catapult current sheet.

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2

Forsyth, C., M. Lester, S. W. H. Cowley, I. Dandouras, A. N. Fazakerley, R. C. Fear, H. U. Frey, et al. "Observed tail current systems associated with bursty bulk flows and auroral streamers during a period of multiple substorms." Annales Geophysicae 26, no. 1 (February 4, 2008): 167–84. http://dx.doi.org/10.5194/angeo-26-167-2008.

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Abstract. We present a multi-instrument study of a substorm bursty bulk flow (BBF) and auroral streamer. During a substorm on 25 August 2003, which was one of a series of substorms that occurred between 00:00 and 05:00 UT, the Cluster spacecraft encountered a BBF event travelling Earthwards and duskwards with a velocity of ~500 km s−1 some nine minutes after the onset of the substorm. Coincident with this event the IMAGE spacecraft detected an auroral streamer in the substorm auroral bulge in the Southern Hemisphere near the footpoints of the Cluster spacecraft. Using FluxGate Magnetometer (FGM) data from the four Cluster spacecraft, we determine the field-aligned currents in the BBF, using the curlometer technique, to have been ~5 mA km−2. When projected into the ionosphere, these currents give ionospheric field-aligned currents of ~18 A km−2, which is comparable with previously observed ionospheric field-aligned currents associated with BBFs and auroral streamers. The observations of the BBF are consistent with the plasma "bubble" model of Chen and Wolf (1993). Furthermore, we show that the observations of the BBF are consistent with the creation of the BBF by the reconnection of open field lines Earthward of a substorm associated near-Earth neutral line.

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3

Herwitz, Daniel, and Gary Shapiro. "Earthwards: Robert Smithson and Art after Babel." Journal of Aesthetics and Art Criticism 56, no. 1 (1998): 78. http://dx.doi.org/10.2307/431956.

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4

Deng, X. H., R. X. Tang, R. Nakamura, W. Baumjohann, T. L. Zhang, P. W. Daly, H. Rème, et al. "Observation of reconnection pulses by Cluster and Double Star." Annales Geophysicae 23, no. 8 (November 8, 2005): 2921–27. http://dx.doi.org/10.5194/angeo-23-2921-2005.

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Abstract. During a reconnection event on 7 August 2004, Cluster and Double Star (TC-1) were near the neutral sheet and simultaneously detected the signatures of the reconnection pulses. AT 22:59 UT tailward flow followed by earthward flow was detected by Cluster at about 15 RE, while earthward plasma flow followed by tailward flow was observed by TC-1 at about 10 RE. During the flow reversal from tailward to earthward, the magnetic field Bz changed sign from mainly negative values to positive, and the X component of the magnetic curvature vector switched sign from the tailward direction to the earthward direction, which indicates that the reconnection site (X-line) moved tailward past the Cluster constellation. By using multi-point analysis and observation of energetic electron and ion flux, we study the movement and structure of the current sheet and discuss the braking effect of the earthward flow bursts in the inner magnetosphere.

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Duan, S. P., Z. X. Liu, J. Liang, Y. C. Zhang, and T. Chen. "Multiple magnetic dipolarizations observed by THEMIS during a substorm." Annales Geophysicae 29, no. 2 (February 15, 2011): 331–39. http://dx.doi.org/10.5194/angeo-29-331-2011.

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Abstract. The magnetic field dipolarization in the vicinity of substorm onset and during substorm expansion phase during the period of 06:00–06:40 UT on 15 February 2008 is investigated with observations from multiple probes of THEMIS. It is found that the magnetic dipolarization at the substorm onset (the onset time was about 06:14 UT) was not accompanied by obvious magnetic disturbance and ion bulk speed variation. The magnetic dipolarizations taking place during the substorm expansion phase observed by P4~(−10.97, 2.04, −3.03) RE and P3~(−11.32, 1.15, −3.10) RE were mostly accompanied by high speed earthward ion bulk flow, but the magnetic dipolarizations occurring during the substorm expansion phase observed by P5~(−9.45, 1.07, −2.85) RE were not accompanied by high speed earthward ion bulk flow. Before substorm onset THEMIS P3, P4, P5 all observed the Bx component fluctuation with a period of about 300 s. After substorm onset earthward high speed ion bulk flow and significant magnetic disturbances both occurred at P3 and P4 locations. These results indicate that there is no one-to-one relationship between the near-Earth magnetic dipolarization and the earthward ion bulk flow. In particular, the magnetic dipolarization occurring on the earthward side of the inner near-Earth plasma sheet is not accompanied by high speed earthward ion bulk flow. The dipolarization at substorm onset is a local and small scale phenomenon. There are multiple magnetic dipolarizations occurring during the substorm expansion phase. The dipolarization process is very complex and is not simply an MHD process. It is accompanied by some kinds of plasma instabilities, the plasma sheet azimuthal expansion not only by earthward ion bulk flow during substorm. A sharp increase of the AE index does not always give an accurate substorm onset time for substorm analysis.

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6

Juusola, Liisa, Sanni Hoilijoki, Yann Pfau-Kempf, Urs Ganse, Riku Jarvinen, Markus Battarbee, Emilia Kilpua, Lucile Turc, and Minna Palmroth. "Fast plasma sheet flows and X line motion in the Earth's magnetotail: results from a global hybrid-Vlasov simulation." Annales Geophysicae 36, no. 5 (September 10, 2018): 1183–99. http://dx.doi.org/10.5194/angeo-36-1183-2018.

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Abstract. Fast plasma flows produced as outflow jets from reconnection sites or X lines are a key feature of the dynamics in the Earth's magnetosphere. We have used a polar plane simulation of the hybrid-Vlasov model Vlasiator, driven by steady southward interplanetary magnetic field and fast solar wind, to study fast plasma sheet ion flows and related magnetic field structures in the Earth's magnetotail. In the simulation, lobe reconnection starts to produce fast flows after the increasing pressure in the lobes has caused the plasma sheet to thin sufficiently. The characteristics of the earthward and tailward fast flows and embedded magnetic field structures produced by multi-point tail reconnection are in general agreement with spacecraft measurements reported in the literature. The structuring of the flows is caused by internal processes: interactions between major X points determine the earthward or tailward direction of the flow, while interactions between minor X points, associated with leading edges of magnetic islands carried by the flow, induce local minima and maxima in the flow speed. Earthward moving flows are stopped and diverted duskward in an oscillatory (bouncing) manner at the transition region between tail-like and dipolar magnetic fields. Increasing and decreasing dynamic pressure of the flows causes the transition region to shift earthward and tailward, respectively. The leading edge of the train of earthward flow bursts is associated with an earthward propagating dipolarization front, while the leading edge of the train of tailward flow bursts is associated with a tailward propagating plasmoid. The impact of the dipolarization front with the dipole field causes magnetic field variations in the Pi2 range. Major X points can move either earthward or tailward, although tailward motion is more common. They are generally not advected by the ambient flow. Instead, their velocity is better described by local parameters, such that an X point moves in the direction of increasing reconnection electric field strength. Our results indicate that ion kinetics might be sufficient to describe the behavior of plasma sheet bulk ion flows produced by tail reconnection in global near-Earth simulations. Keywords. Magnetospheric physics (magnetospheric configuration and dynamics; plasma sheet) – space plasma physics (numerical simulation studies)

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7

HERWITZ, DANIEL. "Gary Shapiro, Earthwards: Robert Smithson and Art After Babel." Journal of Aesthetics and Art Criticism 56, no. 1 (December 1, 1998): 78–79. http://dx.doi.org/10.1111/1540_6245.jaac56.1.0078.

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8

Nakamura, R., A. Retinò, W. Baumjohann, M. Volwerk, N. Erkaev, B. Klecker, E. A. Lucek, I. Dandouras, M. André, and Y. Khotyaintsev. "Evolution of dipolarization in the near-Earth current sheet induced by Earthward rapid flux transport." Annales Geophysicae 27, no. 4 (April 9, 2009): 1743–54. http://dx.doi.org/10.5194/angeo-27-1743-2009.

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Abstract. We report on the evolution of dipolarization and associated disturbances of the near-Earth current sheet during a substorm on 27 October 2007, based upon Cluster multi-point, multi-scale observations of the night-side plasma sheet at X~−10 RE. Three dipolarization events were observed accompanied by activations on ground magnetograms at 09:07, 09:14, and 09:22 UT. We found that all these events consist of two types of dipolarization signatures: (1) Earthward moving dipolarization pulse, which is accompanied by enhanced rapid Earthward flux transport and is followed by current sheet disturbances with decrease in BZ and enhanced local current density, and subsequent (2) increase in BZ toward a stable level, which is more prominent at Earthward side and evolving tailward. During the 09:07 event, when Cluster was located in a thin current sheet, the dipolarization and fast Earthward flows were also accompanied by further thinning of the current sheet down to a half-thickness of about 1000 km and oscillation in a kink-like mode with a period of ~15 s and propagating duskward. Probable cause of this "flapping current sheet" is shown to be the Earthward high-speed flow. The oscillation ceased as the flow decreased and the field configuration became more dipolar. The later rapid flux transport events at 09:14 and 09:22 UT took place when the field configuration was initially more dipolar and were also associated with BZ disturbance and local current density enhancement, but to a lesser degree. Hence, current sheet disturbances induced by initial dipolarization pulses could differ, depending on the configuration of the current sheet.

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9

Wanliss, J. A., R. D. Sydora, G. Rostoker, and R. Rankin. "Origin of some anisotropic tailward flows in the plasma sheet." Annales Geophysicae 20, no. 10 (October 31, 2002): 1559–75. http://dx.doi.org/10.5194/angeo-20-1559-2002.

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Abstract. We use a test particle model to explore anisotropy and fast flows in the central plasma sheet (CPS) that are a consequence of plasma sheet boundary layer (PSBL) ion beam dynamics. Ion distributions and flows (velocity moments) in the CPS and equatorial current sheet (CS) are compared and we find that mirroring of initially earthward beams from the PSBL, and their subsequent convection to the CS region, results in strong anisotropy throughout the CPS. At higher latitudes, velocity moments are field-aligned and feature earthward flow. Deeper in the CPS, velocity moments yield flows in the anti-earthward direction. There is no clear distinction between the PSBL and CPS, since velocity distributions with large streaming components occur throughout the model CPS, but in the CS region they are anisotropic and nongyrotropic. In the CS region velocity moments can feature anti-earthward cross field flows. These tailward flows (> 400 km/s) are observed in the CS region between X = - 20 to - 30 RE due to nonadiabatic effects. Model results suggest that fast tailward plasma flows can be obtained without necessarily appealing to magnetotail processes associated with dynamic geomagnetic activity.Key words. Magnetospheric physics (magnetospheric con-figuration and dynamics) – Space plasma physics (charge particle motion and acceleration; numerical simulation studies)

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10

Peterson, I. "Earthward on a Rocky, Chaotic Course." Science News 128, no. 2 (July 13, 1985): 23. http://dx.doi.org/10.2307/3970030.

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11

Shiokawa, K., A. Ieda, A. Nakajima, K. Sakaguchi, R. Nomura, T. Aslaksen, M. Greffen, et al. "Longitudinal development of a substorm brightening arc." Annales Geophysicae 27, no. 5 (May 4, 2009): 1935–40. http://dx.doi.org/10.5194/angeo-27-1935-2009.

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Abstract. We present simultaneous THEMIS-ground observations of longitudinal (eastward) extension of a substorm initial-brightening arc at Gillam (magnetic latitude: 65.6°) at 08:13 UT on 10 January 2008. The speed of the eastward arc extension was ~2.7 km/s. The extension took place very close to the footprints of the longitudinally separated THEMIS E and D satellites at ~12 RE. The THEMIS satellites observed field dipolarization, weak earthward flow, and pressure increase, which propagated eastward from E to D at a speed of ~50 km/s. The THEMIS A satellite, located at 1.6 RE earthward of THEMIS E, observed fluctuating magnetic field during and after the dipolarization. The THEMIS E/D observations suggest that the longitudinal extension of the brightening arc at substorm onset is caused by earthward flow braking processes which produce field dipolarization and pressure increase propagating in longitude in the near-earth plasma sheet.

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12

Izutsu, T., and M. Fujimoto. "THEMIS observations of plasma transport via eddy diffusion." Annales Geophysicae 30, no. 12 (December 17, 2012): 1703–7. http://dx.doi.org/10.5194/angeo-30-1703-2012.

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Abstract. We provide an event study of THEMIS observations of the low-latitude boundary layer in the dayside magnetosphere. Simultaneous multipoint observations obtained on 5 December 2008 show that the magnetosheath-like plasma in the low-latitude boundary layer is transferred earthward from the magnetopause. This earthward transport is accompanied by decrease in the density and fluctuating bulk flow. We calculate the eddy diffusion coefficients, which can be estimated from the observed velocity data, and found that the numbers are in good quantitative agreement with the spatial and time scales of the observed earthward transport signatures. It is shown that other possible plasma transport processes such as convection or diffusion induced by plasma wave turbulence are inconsistent with the observations. Our study strongly suggests that the observed transport is due to diffusive transport via turbulent eddy motions as is the case of an ordinary (Navier–Stokes) fluid.

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13

Keika, K., R. Nakamura, M. Volwerk, V. Angelopoulos, W. Baumjohann, A. Retinò, M. Fujimoto, et al. "Observations of plasma vortices in the vicinity of flow-braking: a case study." Annales Geophysicae 27, no. 8 (August 4, 2009): 3009–17. http://dx.doi.org/10.5194/angeo-27-3009-2009.

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Abstract. We examine fast plasma flows and magnetic field fluctuations observed by THEMIS at 03:00–03:30 UT on 12 December 2007. All THEMIS probes are situated in the near-Earth plasma sheet (XSM>−10 RE) with 1–2 RE spacecraft separations in azimuthal and radial directions. We focus on the observations of plasma convective flows made simultaneously by more than one THEMIS probe. At about 03:10 UT and 03:14 UT, the THEMIS P2 probe observed earthward flows of >100 km/s. The THEMIS P1 probe, located duskward and earthward of P2, observed tailward flows under a positive Bz. The inner most probe THEMIS P4, located at almost the same MLT as THEMIS P1 and P2, did not see any clear flow. We examine the convective flow patterns for the THEMIS observations. We conclude that plasma vortices are formed near the region where the earthward flows slow down and turn in azimuthal directions.

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14

Wang, R., R. Nakamura, T. Zhang, A. Du, W. Baumjohann, Q. Lu, and A. N. Fazakerley. "Evidence of transient reconnection in the outflow jet of primary reconnection site." Annales Geophysicae 32, no. 3 (March 14, 2014): 239–48. http://dx.doi.org/10.5194/angeo-32-239-2014.

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Abstract. The precise mechanism for the formation of magnetic islands in the magnetotail and the subsequent evolution are still controversial. New investigations have provided the first observational evidence of secondary reconnection in the earthward outflow jet of primary reconnection in the magnetotail. The secondary reconnection takes place 38 c/ωpi earthward from the primary reconnection site and results in the birth of a magnetic island observed. This generation mechanism is different from the widely used model of multiple reconnection X-lines. The duration of the secondary reconnection was approximate one ion gyration period (5 s). The observations resemble recent numerical simulations where magnetic reconnection could spontaneously and transiently happen in the outflow jet, called secondary reconnection, which was used to explain the formation of the dipolarization fronts. Coincidentally, another magnetic island moving earthward passed through three satellites successively. By this chance we find the magnetic island was accelerated towards Earth with an acceleration of about 9 km s−2 at −19 RE in the magnetotail.

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15

Snekvik, K., S. Haaland, N. Østgaard, H. Hasegawa, R. Nakamura, T. Takada, L. Juusola, et al. "Cluster observations of a field aligned current at the dawn flank of a bursty bulk flow." Annales Geophysicae 25, no. 6 (June 29, 2007): 1405–15. http://dx.doi.org/10.5194/angeo-25-1405-2007.

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Abstract. This article describes observations of a bursty bulk flow (BBF) in the outer central plasma sheet. The observations are made with the Cluster satellites, located approximately 19 RE downtail, close to the midnight sector in the Southern Hemisphere. 40–60 s after Cluster first detected the BBF, there was a large bipolar perturbation in the magnetic field. A Grad-Shafranov reconstruction has revealed that this is created by a field-aligned current at the flank of the BBF. Further analysis of the plasma moments has shown that the BBF has the properties of a depleted flux tube. Depleted flux tubes are an important theoretical model for how plasma and magnetic flux can be transported Earthward in the magnetotail as part of the Dungey cycle. The field aligned current is directed Earthward and is located at the dawn side of the BBF. Thus, it is consistent with the magnetic shear at the flank of an Earthward moving BBF. The total current has been estimated to be about 0.1 MA.

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16

Snekvik, K., R. Nakamura, N. Østgaard, S. Haaland, and A. Retinò. "The Hall current system revealed as a statistical significant pattern during fast flows." Annales Geophysicae 26, no. 11 (November 5, 2008): 3429–37. http://dx.doi.org/10.5194/angeo-26-3429-2008.

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Abstract. We have examined the dawn-dusk component of the magnetic field, BY, in the night side current sheet during fast flows in the neutral sheet. 237 h of Cluster data from the plasma sheet between 2 August 2002 and 2 October 2002 have been analysed. The spatial pattern of BY as a function of the distance from the centre of the current sheet has been estimated by using a Harris current sheet model. We have used the average slopes of these patterns to estimate earthward and tailward currents. For earthward fast flows there is a tailward current in the inner central plasma sheet and an earthward current in the outer central plasma sheet on average. For tailward fast flows the currents are oppositely directed. These observations are interpreted as signatures of Hall currents in the reconnection region or as field aligned currents which are connected with these currents. Although fast flows often are associated with a dawn-dusk current wedge, we believe that we have managed to filter out such currents from our statistical patterns.

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17

Kondoh, K., and M. Ugai. "Three-dimensional earthward fast flow in the near-Earth plasma sheet in a sheared field: comparisons between simulations and observations." Annales Geophysicae 27, no. 6 (June 8, 2009): 2297–302. http://dx.doi.org/10.5194/angeo-27-2297-2009.

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Abstract. Three-dimensional configuration of earthward fast flow in the near-Earth plasma sheet is studied using three-dimensional magnetohydrodynamics (MHD) simulations on the basis of the spontaneous fast reconnection model. In this study, the sheared magnetic field in the plasma sheet is newly considered in order to investigate the effects of it to the earthward fast flow, and the results are discussed in comparison with no-shear simulations. The virtual probes located at different positions in our simulation domain in shear/no-shear cases could explain different behavior of fast flows in the real observations.

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18

Fu, H. S., Y. V. Khotyaintsev, A. Vaivads, M. André, and S. Y. Huang. "Occurrence rate of earthward-propagating dipolarization fronts." Geophysical Research Letters 39, no. 10 (May 23, 2012): n/a. http://dx.doi.org/10.1029/2012gl051784.

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19

Ma, YuDuan, JinBin Cao, Henry Reme, Iannis Dandouras, Malcolm Dunlop, and Elisabeth Lucek. "Multi-spacecraft observations of earthward flow bursts." Science China Technological Sciences 55, no. 5 (March 20, 2012): 1305–11. http://dx.doi.org/10.1007/s11431-012-4797-6.

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20

Juusola, L., N. Østgaard, E. Tanskanen, N. Partamies, and K. Snekvik. "Earthward plasma sheet flows during substorm phases." Journal of Geophysical Research: Space Physics 116, A10 (October 2011): n/a. http://dx.doi.org/10.1029/2011ja016852.

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21

YANG, Hong-Ang, and Shu-Ping JIN. "Numerical Study on the Earthward Propagating Plasmoids." Chinese Journal of Geophysics 45, no. 5 (September 2002): 639–53. http://dx.doi.org/10.1002/cjg2.278.

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22

Runov, Andrei, Maxime Grandin, Minna Palmroth, Markus Battarbee, Urs Ganse, Heli Hietala, Sanni Hoilijoki, et al. "Ion distribution functions in magnetotail reconnection: global hybrid-Vlasov simulation results." Annales Geophysicae 39, no. 4 (July 2, 2021): 599–612. http://dx.doi.org/10.5194/angeo-39-599-2021.

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Abstract. We present results of noon–midnight meridional plane global hybrid-Vlasov simulations of the magnetotail ion dynamics under a steady southward interplanetary magnetic field using the Vlasiator model. The simulation results show magnetotail reconnection and formation of earthward and tailward fast plasma outflows. The hybrid-Vlasov approach allows us to study ion velocity distribution functions (VDFs) that are self-consistently formed during the magnetotail evolution. We examine the VDFs collected by virtual detectors placed along the equatorial magnetotail within earthward and tailward outflows and around the quasi-steady X line formed in the magnetotail at X≈-14RE. This allows us to follow the evolution of VDFs during earthward and tailward motion of reconnected flux tubes as well as study signatures of unmagnetized ion motion in the weak magnetic field near the X line. The VDFs indicate actions of Fermi-type and betatron acceleration mechanisms, ion acceleration by the reconnection electric field, and Speiser-type motion of ions near the X line. The simulated VDFs are compared and show good agreement with VDFs observed in the magnetotail by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. We find that the VDFs become more gyrotropic but retain transverse anisotropy and counterstreaming ion beams when being convected earthward. The presented global hybrid-Vlasov simulation results are valuable for understanding physical processes of ion acceleration during magnetotail reconnection, interpretation of in situ observations, and for future mission development by setting requirements on pitch angle and energy resolution of upcoming instruments.

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23

Birn, J., J. Raeder, Y. L. Wang, R. A. Wolf, and M. Hesse. "On the propagation of bubbles in the geomagnetic tail." Annales Geophysicae 22, no. 5 (April 8, 2004): 1773–86. http://dx.doi.org/10.5194/angeo-22-1773-2004.

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Abstract. Using three-dimensional magnetohydrodynamic simulations, we investigate the propagation of low-entropy magnetic flux tubes ("bubbles") in the magnetotail. Our simulations address fundamental properties of the propagation and dynamics of such flux tubes rather than the actual formation process. We find that the early evolution, after a sudden reduction of pressure and entropy on a localized flux tube, is governed by re-establishing the balance of the total pressure in the dawn-dusk and north-south directions through compression on a time scale less than about 20s for the typical magnetotail. The compression returns the equatorial pressure to its original unperturbed value, due to the fact that the magnetic field contributes only little to the total pressure, while farther away from the equatorial plane the magnetic field compression dominates. As a consequence the pressure is no longer constant along a flux tube. The subsequent evolution is characterized by earthward propagation at speeds of the order of 200-400km/s, depending on the initial amount of depletion and the cross-tail extent of a bubble. Simple acceleration without depletion does not lead to significant earthward propagation. It hence seems that both the entropy reduction and the plasma acceleration play an important role in the generation of fast plasma flows and their propagation into the near tail. Earthward moving bubbles are found to be associated with field-aligned current systems, directed earthward on the dawnward edge and tailward on the duskward edge. This is consistent with current systems attributed to observed bursty bulk flows and their auroral effects.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheet)nguage:

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24

Volwerk, M., T. L. Zhang, R. Nakamura, A. Runov, W. Baumjohann, K. H. Glassmeier, T. Takada, et al. "Plasma flow channels with ULF waves observed by Cluster and Double Star." Annales Geophysicae 23, no. 8 (November 8, 2005): 2929–35. http://dx.doi.org/10.5194/angeo-23-2929-2005.

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Abstract. On 14 August 2004 a large-scale magnetic structure was observed by Double Star TC-1 in the southern lobe and by Cluster in the northern lobe of the magnetotail. The structure has the signature of a (localized) dipolarization, decreasing Bx accompanied by an increasing Bz and a strong earthward flow. The propagation direction of this structure, however, seems to be more in the dawnward direction than earthward. The structure is accompanied by ULF waves with a period of ~5 min, which are simultaneously observed by the ground magnetometer station DIK, at the magnetic footpoints of the spacecraft. We interprete these waves as modes driven by the plasma flow and propagating in the flow channel.

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25

Liang, J., F. Jiang, E. Donovan, E. Spanswick, V. Angelopoulos, and R. Strangeway. "Quasi-parallel electron beams and their possible application in inferring the auroral arc's root in the magnetosphere." Annales Geophysicae 31, no. 6 (June 20, 2013): 1077–101. http://dx.doi.org/10.5194/angeo-31-1077-2013.

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Abstract. In this study we investigate the upgoing electron beams at the topside ionosphere and their counterpart feature, the bidirectional quasi-parallel electron beams (QPEB) in the equatorial magnetosphere, with highlight on their potential application in estimating the location of the arc's root (AR) in the magnetotail central plasma sheet (CPS). We infer from FAST data that the upgoing electron beam is often found in the equatorward vicinity of the inverted-V arc. On the premise of such a scenario, we propose a method to estimate the location of the AR from available magnetospheric measurements by assuming that the tailward boundary of the QPEB demarcates the earthward boundary of the AR. We report two events with THEMIS observations of QPEBs in the magnetotail CPS, and demonstrate how to use the QPEB features, together with the magnetic signatures of the current circuit constituted by the QPEB and arc, to estimate the earthward boundary of the AR. We find that the estimated earthward boundary of AR is situated at the periphery of a quasi-dipolar magnetosphere characterized by a strong Bz gradient. This finding is consistent with previously existing proposals on the possible AR location in the tail (e.g., Lui and Burrows, 1978; Sergeev et al., 2012).

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26

Schmid, D., M. Volwerk, R. Nakamura, W. Baumjohann, and M. Heyn. "A statistical and event study of magnetotail dipolarization fronts." Annales Geophysicae 29, no. 9 (September 8, 2011): 1537–47. http://dx.doi.org/10.5194/angeo-29-1537-2011.

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Abstract. A study of dipolarization fronts of the Earth's magnetotail has been performed using seven years (2001–2007) of Cluster data. Events both with and without high-speed earthward flows are included. A superposed epoch analysis of the data shows that the dipolarization is preceeded by a decrease of Bz before the increase. The duration of the dipolarization tends to be decreasing with increasing velocity of the plasma flows. The thickness of the dipolarization front is on average 1.8 plasma inertial lengths, independent of the plasma velocity. We find that the events fall into two categories: Earthward and tailward moving dipolarizations. The dipolarization fronts can be assumed to be tangential discontinuities and the currents on the front have mainly a perpendicular component.

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Kim, R. ‐S, K. ‐S Cho, K. ‐H Kim, Y. ‐D Park, Y. ‐J Moon, Y. Yi, J. Lee, H. Wang, H. Song, and M. Dryer. "CME Earthward Direction as an Important Geoeffectiveness Indicator." Astrophysical Journal 677, no. 2 (April 20, 2008): 1378–84. http://dx.doi.org/10.1086/528928.

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Zhou, X. Z., V. Angelopoulos, V. A. Sergeev, and A. Runov. "Accelerated ions ahead of earthward propagating dipolarization fronts." Journal of Geophysical Research: Space Physics 115, A5 (May 2010): n/a. http://dx.doi.org/10.1029/2010ja015481.

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29

Nakamura, R., W. Baumjohann, R. Schödel, M. Brittnacher, V. A. Sergeev, M. Kubyshkina, T. Mukai, and K. Liou. "Earthward flow bursts, auroral streamers, and small expansions." Journal of Geophysical Research: Space Physics 106, A6 (June 1, 2001): 10791–802. http://dx.doi.org/10.1029/2000ja000306.

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30

Ma, YuDuan, JinBin Cao, H. Reme, I. Dandouras, E. Lucek, and M. Dunlop. "The radial evolution of earthward BBFs during substorm." Science China Earth Sciences 53, no. 10 (August 31, 2010): 1542–51. http://dx.doi.org/10.1007/s11430-010-4040-x.

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31

Zhang, L. Q., J. Y. Wang, W. Baumjohann, H. Rème, and M. W. Dunlop. "Earthward and tailward flows in the plasma sheet." Journal of Geophysical Research: Space Physics 120, no. 6 (June 2015): 4487–95. http://dx.doi.org/10.1002/2015ja021154.

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32

Draper, N. C., M. Lester, S. W. H. Cowley, J. A. Wild, S. E. Milan, G. Provan, A. Grocott, et al. "Cluster magnetotail observations of a tailward-travelling plasmoid at substorm expansion phase onset and field aligned currents in the plasma sheet boundary layer." Annales Geophysicae 23, no. 12 (December 23, 2005): 3667–83. http://dx.doi.org/10.5194/angeo-23-3667-2005.

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Abstract. We present data from both ground- and space-based instruments for a substorm event which occurred on 5 October 2002, with an expansion phase onset time of 02:50 UT determined from the ground magnetometer data. During this substorm, the Cluster spacecraft were located around 15 RE downtail, 8 RE from midnight in the pre-midnight sector and just 2 RE above the equatorial plane (in GSM coordinates). At expansion phase onset the Cluster spacecraft were located in the plasma sheet, tailward of a near-Earth neutral line and detected a significant time delay of 6 min between the tail field Bz component becoming negative and the subsequent detection of Earthward flows. This is explained by the formation of a tailward-directed travelling compression region initially Earthward of the spacecraft; 7 min later the Cluster spacecraft entered the plasma sheet boundary layer; they remained in and close to the plasma sheet boundary layer for around 15 min before exiting to the lobe. The spacecraft then re-entered the plasma sheet 30 min after onset. Earthward then tailward directed currents detected in the plasma sheet boundary layer after onset indicate that the Cluster spacecraft encountered the dawnward and duskward portions of the reconnection flow associated current system with Region 1 sense, respectively. The reconnection site and current system were initially skewed towards the pre-midnight sector, consistent with previous observations that found the majority of substorm onsets located in this sector. At later times the reconnection site and current system had moved towards dawn, to be located more centrally in the midnight sector.

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33

Borodkova, N. L., A. G. Yahnin, K. Liou, J. A. Sauvaud, A. O. Fedorov, V. N. Lutsenko, M. N. Nozdrachev, and A. A. Lyubchich. "Plasma sheet fast flows and auroral dynamics during substorm: a case study." Annales Geophysicae 20, no. 3 (March 31, 2002): 341–47. http://dx.doi.org/10.5194/angeo-20-341-2002.

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Abstract. Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL). It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region) is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs), described by Angelopolous et al. (1992). These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i) tailward/earthward flows were superimposed on a very strong duskward flow, and (ii) wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.Key words. Magnetospheric physics (auroral phenomena; plasma sheet; storms and substorms)

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34

Sander-Regier, Renate. "Earthways: Opportunity, Community and Meaning in the Personal Garden." Brock Review 10, no. 1 (September 24, 2008): 1–20. http://dx.doi.org/10.26522/br.v10i1.41.

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The hybrid space of the personal garden offers valuable opportunities for individuals to express themselves personally in an outdoor setting, to develop meaningful relationships with green spaces, and to connect with the greater natural environment and urban community, as demonstrated in the works of contemporary gardener-authors Marjorie Harris, Sara Stein, and Leon Whiteson. These opportunities are particularly significant in urban environments where access to nature and green space is limited, and where gardening activities can contribute to the health of the natural environment, the wellbeing of people involved in the space, and the vitality of the community at large.

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35

Zong, Q. G., S. Y. Fu, D. N. Baker, M. L. Goldstein, P. Song, J. A. Slavin, T. A. Fritz, et al. "Earthward flowing plasmoid: Structure and its related ionospheric signature." Journal of Geophysical Research: Space Physics 112, A7 (July 2007): n/a. http://dx.doi.org/10.1029/2006ja012112.

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36

Ohtani, Shin-ichi. "Earthward expansion of tail current disruption: Dual-satellite study." Journal of Geophysical Research: Space Physics 103, A4 (April 1, 1998): 6815–25. http://dx.doi.org/10.1029/98ja00013.

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37

Petrukovich, A. A., W. Baumjohann, R. Nakamura, R. Schödel, and T. Mukai. "Are earthward bursty bulk flows convective or field-aligned?" Journal of Geophysical Research: Space Physics 106, A10 (October 1, 2001): 21211–15. http://dx.doi.org/10.1029/2001ja900019.

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38

Zhang, Lingqian, Jiye Wang, Zhenxing Liu, and Jiankui Shi. "Earthward Convective Bursty Flows in the Center Plasma Sheet." Chinese Journal of Space Science 31, no. 1 (2011): 20. http://dx.doi.org/10.11728/cjss2011.01.020.

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39

Grigorenko, Elena E., Andrey Y. Malykhin, Elena A. Kronberg, and Evgeny V. Panov. "Quasi-parallel Whistler Waves and Their Interaction with Resonant Electrons during High-velocity Bulk Flows in the Earth’s Magnetotail." Astrophysical Journal 943, no. 2 (February 1, 2023): 169. http://dx.doi.org/10.3847/1538-4357/acaf52.

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Abstract In collisionless space, plasma waves are important channels of energy conversion, affecting the local particle velocity distribution functions through wave–particle interactions. In this paper we present a comparative statistical analysis of the characteristics of quasi-parallel narrowband whistler waves and the properties of resonant electrons interacting with these waves during the intervals of earthward and tailward high-velocity bulk flows produced by the near-Earth X-line and observed by Magnetospheric Multiscale Mission spacecraft. We found that on both sides of the X-line, the suprathermal electrons (≥1 keV) having large pitch angles make the major contribution to the maximal growth rate (γ) of these waves. The whistler waves were observed almost simultaneously with strong enhancements of perpendicular magnetic gradients localized at electron scales near dipolarization fronts associated with the earthward bulk flows, and near flux ropes/magnetic islands embedded into the tailward bulk flows. Betatron energization of electrons due to the appearance of such gradients increases the perpendicular anisotropy of electron distribution, which could be responsible for the whistler wave generation. We found that in the course of electron interactions with the whistler waves the lower-energy resonant electrons can transfer a part of their kinetic energy to the higher-energy electrons, especially in the Central Plasma Sheet. This results in formation/enhancement of energy-dependent perpendicular anisotropy and power-law tails in the high-energy range of electron velocity distribution. We conclude that despite the differences in the magnetic structure of the earthward and tailward bulk flows, the mechanisms of the quasi-parallel whistler wave generation and the properties of resonant electrons are quite similar.

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40

Schödel, R., K. Dierschke, W. Baumjohann, R. Nakamura, and T. Mukai. "The storm time central plasma sheet." Annales Geophysicae 20, no. 11 (November 30, 2002): 1737–41. http://dx.doi.org/10.5194/angeo-20-1737-2002.

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Abstract. The plasma sheet plays a key role during magnetic storms because it is the bottleneck through which large amounts of magnetic flux that have been eroded from the dayside magnetopause have to be returned to the dayside magnetosphere. Using about five years of Geotail data we studied the average properties of the near- and midtail central plasma sheet (CPS) in the 10–30 RE range during magnetic storms. The earthward flux transport rate is greatly enhanced during the storm main phase, but shows a significant earthward decrease. Hence, since the magnetic flux cannot be circulated at a sufficient rate, this leads to an average dipolarization of the central plasma sheet. An increase of the specific entropy of the CPS ion population by a factor of about two during the storm main phase provides evidence for nonadiabatic heating processes. The direction of flux transport during the main phase is consistent with the possible formation of a near-Earth neutral line beyond ~20 RE.Key words. Magnetospheric physics (plasma convection; plasma sheet; storms and substorms)

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41

Green, James Lauer, and James L. Horwitz. "Destiny of earthward streaming plasma in the plasmasheet boundary layer." Geophysical Research Letters 13, no. 1 (January 1986): 76–79. http://dx.doi.org/10.1029/gl013i001p00076.

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42

Shue, J. H., A. Ieda, A. T. Y. Lui, G. K. Parks, T. Mukai, and S. Ohtani. "Two classes of earthward fast flows in the plasma sheet." Journal of Geophysical Research: Space Physics 113, A2 (February 2008): n/a. http://dx.doi.org/10.1029/2007ja012456.

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43

Scholer, Manfred. "Earthward plasma flow during near-Earth magnetotail reconnection: Numerical simulations." Journal of Geophysical Research 92, A11 (1987): 12425. http://dx.doi.org/10.1029/ja092ia11p12425.

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44

Murray, Carl D. "Meterorites: Earthward bound from chaotic regions of the asteroid belt." Nature 315, no. 6022 (June 1985): 712. http://dx.doi.org/10.1038/315712a0.

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45

Ukhorskiy, A. Y., M. I. Sitnov, V. G. Merkin, and A. V. Artemyev. "Rapid acceleration of protons upstream of earthward propagating dipolarization fronts." Journal of Geophysical Research: Space Physics 118, no. 8 (August 2013): 4952–62. http://dx.doi.org/10.1002/jgra.50452.

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46

Nemecek, Z., A. Fedorov, J. Safrankova, and G. Zastenker. "Structure of the low-latitude magnetopause: MAGION-4 observations." Annales Geophysicae 15, no. 5 (May 31, 1997): 553–61. http://dx.doi.org/10.1007/s00585-997-0553-9.

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Abstract. The aims of this paper are (1) briefly to describe the plasma devices onboard the MAGION-4 satellite, launched on 3 August 1995, of the INTERBALL project, and (2) to discuss first observations made near the magnetopause region. During the presented boundary crossings the MAGION-4 observed quasi-periodic pulses of magnetosheath-like plasma in a region of low plasma density. This region is located just earthwards of the magnetopause and is populated by a plasma which, except for the density, has the same parameters as in the magnetosheath. Deeper in the magnetosphere, the encounter of a layer of hot electrons and high-energy ions was interpreted as low-latitude boundary layer.

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47

Burman, Chaim. "When Truth Is »Hurled Earthwards«: Manuscript Variants and Coherentist Truth-Conceptions in Contemporary Rabbinic Discourse." Jewish Studies Quarterly 30, no. 1 (2023): 87. http://dx.doi.org/10.1628/jsq-2023-0006.

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48

Huang, T., H. Wang, J. H. Shue, L. Cai, and G. Pi. "The dayside magnetopause location during radial interplanetary magnetic field periods: Cluster observation and model comparison." Annales Geophysicae 33, no. 4 (April 2, 2015): 437–48. http://dx.doi.org/10.5194/angeo-33-437-2015.

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Abstract. The present work has investigated the midlatitudinal magnetopause locations under radial interplanetary field (RIMF) conditions. Among 262 (256) earthward (sunward) RIMF events from years of 2001 to 2009, Cluster satellites have crossed the magnetopause 22(12) times, with 10 (7) events occurring at midlatitudes. The observed midlatitudinal magnetopause positions are compared with two empirical magnetopause models (Shue et al., 1998; Boardsen et al., 2000) (hereafter referred to as the Shue98 model and the Boardsen00 model). The observation–model differences exhibit local time asymmetry. For earthward RIMF cases, the Shue98 model underestimates the magnetopause positions in the postnoon sector, while it overestimates the magnetopause positions in the dawn and dusk sectors. The Boardsen00 model generally underestimates the magnetopause after 6 MLT (magnetic local time), with larger deviations in the postnoon sector as compared to those in the prenoon. For sunward RIMF cases, the selected events are mainly clustered around the dawn and dusk sectors. The comparison with the Shue98 model indicates contractions in the dawn and expansions in the dusk sector, while the comparison with Boardsen00 indicates general expansions, with larger expansions in the later local time sectors. The local time variations in the differences between observations and the Shue98 and the Boardsen00 models indicate that the real magnetopause could be asymmetrically shaped during radial IMF periods, which should be considered by magnetopause models. The observation–model differences in the magnetopause positions (Δ RMP) during RIMF periods correlate well with the solar wind dynamic pressure, with larger Δ RMP for larger Pd. The southern magnetopause expands further outward relative to the model prediction when the dipole tilt angle is more negative (local summer in the Southern Hemisphere). For earthward RIMF cases, the generally good correlations between Δ RMP and the IMF cone angle are consistent with the previous hypothesis (Dušík et al., 2010) that, with more radial IMF, the subsolar magnetopause will expand further outward, owever, this is not the case for the comparison with Boardsen00 during sunward IMF periods, as it shows less dependence on the IMF cone angle.

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49

Zelenyi, L. M., A. V. Artemyev, and A. A. Petrukovich. "Earthward electric field in the magnetotail: Cluster observations and theoretical estimates." Geophysical Research Letters 37, no. 6 (March 2010): n/a. http://dx.doi.org/10.1029/2009gl042099.

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50

Minami, S., A. I. Podgorny, and I. M. Podgorny. "Laboratory evidence of earthward electric field in the magnetotail current sheet." Geophysical Research Letters 20, no. 1 (January 8, 1993): 9–12. http://dx.doi.org/10.1029/92gl02492.

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