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Dayside Transient Phenomena and Their Impact on the Magnetosphere-Ionosphere

Goal: ISSI-BJ International Team

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Gabor Facskó
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We use a global magnetohydrodynamics simulation to analyze transient magnetic reconnection processes at the magnetopause. The solar wind conditions have been kept constant and an interplanetary magnetic field (IMF) with large duskward BY and southward BZ components has been imposed. Five flux transfer events (FTEs) with clear bipolar magnetic field signatures have been observed. We observed a peculiar structure defined as interlinked flux tubes (IFTs) in the first and fourth FTE, which had very different generation mechanisms. The first FTE originates as an IFTs and remains with this configuration until its final moment. However, the fourth FTE develops as a classical flux rope but changes its 3D magnetic configuration to that of IFTs. This work studies the mechanism for generating IFTs. The growth of the resistive tearing instability has been identified as the cause for the first IFTs formation. We believe that the instability has been triggered by the accumulation of IMF at the subsolar point where the grid resolution is very high. The evidence shows that two new reconnection lines form northward and southward of the subsolar region. The IFTs has been generated with all the classical signatures of a single flux rope. The other IFTs detected in the fourth FTE developed as a result of magnetic reconnection inside its complex and twisted magnetic fields, which leads to a change in the magnetic configuration from a flux rope of twisted magnetic field lines to IFTs.
This study reports observations of energetic ions upstream of the Earth's quasi-parallel bow shock by Cluster at times when interspacecraft separation distances were large. We analyze two individual upstream ion events during high solar wind velocity conditions to compare the spatial evolution of partial energetic ion densities in front of the Earth's bow shock along the magnetic field line. Using a bow shock model, we determine the distance of SC1 and SC3 to the bow shock surface parallel to the magnetic field. The CIS-HIA instrument on board Cluster provides partial energetic ion densities in four energy channels between 10 and 32 keV. Using the differences of the partial energetic ion densities observed on SC1 and SC3, and the distances of the spacecraft to the bow shock, we determine the spatial gradient of partial energetic ion densities at various distances from the bow shock. We show, for the first time, that the e-folding distance and the diffusion coefficient of the diffuse ions become unusually small when these ions interact with high-intensity waves generated by a strong field-aligned beam. © 2018. The American Astronomical Society. All rights reserved..
Gabor Facskó
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ISSI-BJ International Team
 
Gabor Facskó
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Gabor Facskó
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Blanco-Cano et al. (2018) intended to find a type of transient event in the solar wind before the terrestrial bow shock using a special type of simulation. However, the simulation results cannot reproduce the main features of the event. Not only are the physical indicators missing from the simulation result, but the footprints and the signs of the event formation processes too. Based on the remarks described below, I am sure that the features in the simulations are not those type of events.
Gabor Facskó
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If something is not hot and it has not anomalous flow then it is not possible to call spontaneous h-o-t f-l-o-w a-n-o-m-a-l-y Original paper: https://www.ann-geophys.net/36/1081/2018/
Gabor Facskó
added 2 research items
Tangential discontinuties (TDs) are usually considered as thin planar current sheets frozen in the solar wind flow. Previous studies based on the magnetic field measurements onboard of ACE, Wind, and STEREO A, and B proved that this hypotesis is not valid. The curvature of the TDs were determined in several cases. After applying minimum variance and the cross product methods for Ulysses, ACE and STEREO A and B magnetometer measurements, numerous TDs are identified in 2008 and 2009. The time shift of the TD observations is determinated by correlation analysis of the solar wind speed and the magnetic field variations. The 3D topology of the TD is then determinated in some special cases when the four spacecraft are on the same side of the Sun. After fitting a simple model, the location of the TD formation region can be outlined.
Several hot flow anomaly (HFA) like events were observed by STEREO magnetometer (MAG) and solar wind thermal proton (PLASTIC) and electron (SWEA) instruments during the Earth orbit phase of STEREO B in February-March, 2007. The magnetic signature of the tangential discontinuities (TDs) was observed but the resolution of PLASTIC is not sufficient to identify the events without any doubt. The events are identified using the simultaneous measurements of the Cluster fluxgate magnetometer (FGM), ion (CIS/HIA) and resonance sounder (WHISPER) instruments. No HFA events were observed so far from the Earth before and these events are in the very late phase of HFA development. The comparison of these events using data acquired by Cluster and STEREO is a unique opportunity for studying the HFA characteristics far from its generation region, its turbulent features and its spatial-temporal development.
Gabor Facskó
added a research item
Several hot flow anomaly (HFA) like events were observed by STEREO during its Earth orbit phase in November-December 2006 and in the far tail beyond the orbit of the Moon in February-March, 2007. The magnetic signature of the tangential discontinuities was visible, but the resolution of the plasma ion data is not sufficient for our analysis, so a method is thus given to identify HFAs without solar wind velocity measurements. The ejected beam and the current sheet of the young-HFA events were not situated in the same plane according to the results of the hybrid HFA simulations. These very far HFA event observations confirm the previous simulations and theories that the HFAs have a large extent in the direction of the current sheet. The event observed in the geotail suggests that the lifetime of the HFAs might be much longer than expected.