ST2.1

Fast plasma flows (magnetosheath jets) are localized and transient dynamic pressure enhancements found downstream of the Earth’s bow shock, in the magnetosheath region. They can be attributed to density and/or density enhancements and they are an energetic manifestation of the solar wind-magnetosphere coupling. They have been associated to several phenomena such as magnetopause reconnection, direct magnetosphere plasma inflow and the energization of the outer radiation belt electrons.

In this work, we are investigating the properties of a dataset of 9196 jets found by Magnetospheric Multiscale (MMS) from 09/2015 to 09/2020. These jets are classified into different classes based on their associated bow shock configuration. From the full dataset, about 300 jets are distinguished by being in very close proximity to a bow shock transition.

This subset of jet is then carefully pre-processed and statistically analyzed, providing information regarding the likelihood of existent (bow shock ripples, SLAMS penetration) and newly proposed (magnetic reconnection, magnetic islands) generation mechanisms for these jets. The initial results of these events support the pre-existing generation mechanism while giving indications to other possible effects that may take place.

How to cite: Raptis, S., Karlsson, T., Plaschke, F., Kullen, A., and Lindqvist, P.-A.: Fast Plasma Flows Downstream of the Bow Shock Using MMS: Correlations and Generation Mechanisms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8039, https://doi.org/10.5194/egusphere-egu21-8039, 2021.

Dayside magnetic reconnection at the magnetopause, which is a major driver of space weather, is studied for the first time in a three-dimensional (3D) realistic setup using the Vlasiator hybrid-Vlasov kinetic model. A noon–midnight meridional plane simulation is extended in the dawn–dusk direction to cover 7 Earth radii. The southward interplanetary magnetic field causes magnetic reconnection to occur at the subsolar magnetopause. Perturbations arising from kinetic instabilities in the magnetosheath appear to modulate the reconnection. Its characteristics are consistent with multiple, bursty, and patchy magnetopause reconnection. It is shown that the kinetic behavior of the plasma, as simulated by the model, has consequences on the applicability of methods such as the four-field junction to identify and analyse magnetic reconnection in 3D kinetic simulations.

How to cite: Pfau-Kempf, Y., Palmroth, M., Johlander, A., Turc, L., Alho, M., Battarbee, M., Grandin, M., Dubart, M., and Ganse, U.: Hybrid-Vlasov modelling of three-dimensional dayside magnetopause reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13054, https://doi.org/10.5194/egusphere-egu21-13054, 2021.

Topological configurations of the magnetic field play key roles in the evolution of space plasmas. This paper presents a novel algorithm that can estimate the quadratic magnetic gradient as well as the complete geometrical features of magnetic field lines, based on magnetic field and current density measurements by a multiple spacecraft constellation at 4 or more points. The explicit estimators for the linear and quadratic gradients, the apparent velocity of the magnetic structure and the curvature and torsion of the magnetic field lines can be obtained with well predicted accuracies. The feasibility and accuracy of the method have been verified with thorough tests. The algorithm has been successfully applied to exhibit the geometrical structure of a flux rope. This algorithm has wide applications for uncovering a variety of magnetic configurations in space plasmas.

How to cite: Shen, C., Zhang, C., Rong, Z., Pu, Z., Dunlop, M. A., Escoubet, C., Russell, C., Zeng, G., Ren, N., Burch, J., and Zhou, Y.: The Quadratic Magnetic Gradient and Complete Geometry of Magnetic Field Lines Deduced from Multiple Spacecraft Measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-530, https://doi.org/10.5194/egusphere-egu21-530, 2021.

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 (< 440 Myr), the Earth surface was directly exposed to the solar wind during coronal mass ejections (assuming today´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.

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.

How to cite: Varela Rodriguez, J., Brun, S. A., Strugarek, A., Réville, V., Pantellini, F., and Zarka, P.: 3D MHD study of the Earth magnetosphere response during extreme space weather conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1684, https://doi.org/10.5194/egusphere-egu21-1684, 2021.

The ring current is an important part of the large-scale magnetosphere-ionosphere current system; mainly concentrated in the equatorial plane, between 2-7 R_E, and strongly ordered between ± 30 ° latitude. The morphology of ring current directly affects the geomagnetic field at low to middle latitudes. Rapid changes in ring current densities can occur during magnetic storms/sub-storms. Traditionally, the Dst index is used to characterize the intensity of magnetic storms and to reflect the variation of ring current intensity, but this index does not reflect the MLT distribution of ring current. In fact, the ring current has significant variations with MLT, depending on geomagnetic activity, due to the influence of multiple factors; such as, the partial ring current, region 1/region 2 field-aligned currents, the magnetopause current and sub-storm cycle (magnetotail current). The form of the ring current has been inferred from the three-dimensional distribution of ion differential fluxes from neutral atom imaging; however, this technique can not directly obtain the current density distribution (as can be obtained using multi-spacecraft in situ data). Previous in situ estimates of current density have used: Cluster, THEMIS and other spacecraft groups to study the distribution of the ring current for limited ranges of either radial profile, or MLT and MLAT variations. Here, we report on an extension to these studies using FGM data from MMS obtained during the period September 1, 2015 to December 31, 2016, when the MMS orbit and configuration provided good coverage. We employ the curlometer method to calculate the current density, statistically, to analysis the MLT distribution according to different geomagnetic conditions. Our results show the clear asymmetry of the ring current and its different characteristics under different geomagnetic conditions.

How to cite: Tan, X., Dunlop, M., Dong, X., Yang, Y., and Russell, C.: The MLT distribution and detailed structure of ring current:  MMS observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3730, https://doi.org/10.5194/egusphere-egu21-3730, 2021.

Transpolar arcs (TPAs) are predicted by many models to appear in both hemispheres, as so-called conjugate TPAs. However, some observations have suggested that this is not always the case, and that there is an IMF B_x dependence on whether TPAs appear on both hemispheres or not. Specifically, it has been suggested that TPAs only appear on the northern hemisphere for negative IMF B_X and vice versa for positive IMF B_X. Furthermore, a positive Earth dipole tilt is predicted to have a similar effect on TPA occurrences as a negative IMF B_X and vice versa. It is also known that TPAs appear on different locations on the auroral oval, i.e., dawn-, dusk- or both sides of the oval, depending on IMF B_Y. However, the role of IMF B_X and IMF B_Z for the TPA location remains unclear, with some previous observations suggesting a correlation with IMF B_X.

In this study, we investigate the influence of IMF B_X and dipole tilt on TPAs by statistically analyzing observational data. We analyze TPA datasets from four previous studies, as well as our own TPA dataset, created from DMSP satellite measurements. At first glance, the data suggests that there is a strong correlation between both IMF B_X and dipole tilt, and TPA observations in a specific hemisphere. However, when normalizing the data to the solar wind distribution and when taking observational bias into account, this correlation disappears. We therefore conclude that there is no clear correlation between neither IMF B_X nor dipole tilt and in which hemisphere a TPA appears. We further analyze four of the five datasets with respect to dawn-dusk appearances of TPAs and its correlation to IMF B_X, B_Y and B_Z. Here, the results for the datasets mostly agree with previous observations. Finally, we discuss the potential causes for the few non-conjugate TPAs, by studying our own TPA dataset in further detail.

How to cite: Thor, S., Kullen, A., and Cai, L.: IMF BX and Dipole Tilt Dependence on Transpolar Arcs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1780, https://doi.org/10.5194/egusphere-egu21-1780, 2021.

First results are presented of reconstructing the evolution of magnetospheric configurations through the full cycle of isolated substorms. The modeling covers the low- and mid-latitude magnetosphere in the range of radial distances from 2 to 20 Re and is based on a synthesis of (1) a high-resolution representation of the magnetic field by cylindrical basis functions, (2) the ever largest pool of magnetospheric and interplanetary data spanning the last quarter century (1995-2019), (3) an archive of concurrent ground-based indices and their temporal trends, quantifying the geomagnetic activity over the full range of latitudes, including the low-latitude ring current SMR-index, the midlatitude positive bay MPB-index, the auroral SML-index, and the polar cap PC-index, (4) the data-mining nearest-neighbour (NN) technique of the data selection and weighting in the geometric and parametric spaces. The obtained successive diagrams of magnetic depression/compression, electric current, and field line maps demonstrate all the typical features of the substorm cycle: the initial relatively slow stretching of the nightside tail during the growth phase, followed by its sudden collapse associated with a dramatic disruption of the tail current at R~11-16 Re, and finally a gradual recovery of the configuration after the expansion phase is over.

How to cite: Tsyganenko, N., Andreeva, V., Sitnov, M., Gjerloev, J., Chu, X., and Troshichev, O.: Magnetospheric reconfiguration during the substorm cycle as inferred from the data-based modeling., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-809, https://doi.org/10.5194/egusphere-egu21-809, 2021.

Magnetic reconnection is a key fundamental process in collisionless plasmas that explosively converts magnetic energy to plasma kinetic and thermal energies through a change of magnetic field topology in an electron-scale central region called the electron diffusion region. Past simulations and observations demonstrated that this process causes efficient energy conversion through the formation of multiple macro-scale or micro-scale magnetic islands/flux ropes. However, how these different spatiotemporal scale phenomena are coupled is still poorly understood. In this study, to investigate the turbulent evolution of magnetic reconnection, we perform a new large-scale fully kinetic simulation of a thin current sheet considering a power-law spectrum of initial fluctuations in the magnetic field as frequently observed in the Earth’s magnetotail. The simulation demonstrates that during a macro-scale evolution of turbulent reconnection, the merging of macro-scale islands results in reduction of the rate of reconnection as well as the aspect ratio of the electron diffusion region. This allows the repeated, quick formation of new electron-scale islands within the electron diffusion region, leading to an efficient energy cascade between macro- and micro-scales. The simulation also demonstrates that a strong electron acceleration/heating occurs during the micro-scale island evolution within the EDR. These new findings indicate the importance of non-steady features of the EDR to comprehensively understand the energy conversion and cascade processes in collisionless reconnection.

How to cite: Nakamura, T., Hasegawa, H., Phan, T., Genestreti, K., Denton, R., and Nakamura, R.: Micro-scale tearing mode turbulence in the diffusion region during macro-scale evolution of turbulent reconnection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-827, https://doi.org/10.5194/egusphere-egu21-827, 2021.

In July 2017, the MMS constellation was evolving in the magnetotail with an apogee of 25 Earth radii and an average inter-satellite distance of 10 km (i.e. at electron scales). On 23 rd of July around 16:19 UT, MMS was located at the edge of the current sheet which was in a quasi-static state. Then, MMS
suddenly entered in the central plasma sheet and detected the local onset of a small substorm as indicated by the AE index (~400 nT). Fast earthward plasma flows were measured for about 1 hour starting with a period of quasi-steady flow and followed by a saw-tooth like series of plasma jets (“bursty bulk flows”). In the present study, we focus on a short sequence related to an ion scale current sheet crossing embedded in a fast earthward flow. We analyse in detail two other kinetic structures in the vicinity of this current sheet: an ion-scale flux rope and an electron vortex magnetic hole and discuss the Ohm’s law and conversion energy processes.

How to cite: Le Contel, O., Retino, A., Alexandrova, A., Nakamura, R., Alqeeq, S., Chust, T., Mirioni, L., Catapano, F., Jacquey, C., Toledo, S., Stawarz, J., Goodrich, K., Gershman, D. J., Fuselier, S. A., Mukherjee, J., Ahmadi, N., Graham, D., Argall, M., Fischer, D., and Huang, S. and the MMS team: Multiscale analysis of a current sheet embedded in a fast earthward flow during a substorm event detected by MMS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14350, https://doi.org/10.5194/egusphere-egu21-14350, 2021.

In the present work, we consider four dipolarization front (DF) events detected by MMS spacecraft in the Earth’s magnetotail during a substorm on 23rd of July 2017 between 16:05 and 17:19 UT. From their ion scale properties, we show that these four DF events embedded in fast Earthward plasma flows have classical signatures with increases of Bz, velocity and temperature and a decrease of density across the DF. We compute and compare current densities obtained from magnetic and particle measurements and analyse the Ohm’s law. Then we describe the wave activity related to these DFs. We investigate energy conversion processes via J.E calculations and estimate the importance of the electromagnetic energy flow by computing the divergence of the Poynting vector. Finally we discuss the electromagnetic energy conservation in the context of these DFs.

How to cite: Alqeeq, S., Le Contel, O., Canu, P., Retino, A., Chust, T., Alexandrova, A., Mirioni, L., Baraka, S., Richard, L., Khotyaintsev, Y., Nakamura, R., Wilder, F., Ahmadi, N., Wei, H., Argall, M., Fischer, D., Gershman, D., Burch, J., Torbert, R., and Giles, B. and the MMS Team: Investigation of energy conversion processes and wave activity related to dipolarization fronts observed by MMS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11118, https://doi.org/10.5194/egusphere-egu21-11118, 2021.