7 research outputs found
Propagation of a shock-related disturbance in the Earth's magnetosphere
The Grand Unified Magnetosphere-Ionosphere Coupling Simulation, version 4, magnetohydrodynamic simulation of the interplanetary shock event on 9 November 2002 is used to determine the shock-associated disturbance propagation characteristics inside the Earth's magnetosphere. Interaction of an interplanetary fast forward shock with the magnetopause caused a shock-related disturbance inside the magnetosphere that propagated at a speed significantly higher than that in the solar wind or magnetosheath. The propagation direction of the disturbance was calculated from the Rankine-Hugoniot conditions, velocity and magnetic coplanarity, and minimum variance analysis and is shown to vary in different regions of the magnetosphere. Furthermore, the impulse disturbance wave mode changes as the plasma and field conditions change inside the magnetosphere. These results bring important new information about the propagation processes that is not directly obtainable from point measurements made by (even several) spacecraft. On the other hand, comparison of ionospheric observations from the IMAGE magnetometer chain with geosynchronous data allow us to also interpret the double step structure observed at dayside geosynchronous orbit, which is below the simulation resolution. This combination provides us with quite a complete view on shock propagation inside the magnetosphere.Peer reviewe
Analysis of the substructure within a complex magnetic cloud on 3-4 September 2008
In this paper we have analyzed a substructure found within a leading part of a north–south-oriented magnetic cloud (MC) observed on 3–4 September 2008 in the near-Earth solar wind by multiple spacecraft (ACE, Wind, THEMIS B and C). The MC was preceded by a stream interface (SI) and followed by a high-speed stream (HSS). The identified substructure featured a strong depletion of suprathermal halo electrons and showed distinct magnetic field and plasma signatures. It occurred where suprathermal electron flow within a cloud changed from bidirectional to unidirectional, indicating change in the field line connectivity to the Sun. We found that the substructure maintained roughly its integrity from the first Lagrangian point to the vicinity of the Earth's bow shock in the front edge of the MC, but revealed small changes in the structure which could be explained either by temporal evolution or spatial configuration of the spacecraft.Peer reviewe
Sources of the Slow Solar Wind During the Solar Cycle 23/24 Minimum
We investigate the characteristics and the sources of the slow (< 450 km/s)
solar wind during the four years (2006-2009) of low solar activity between
Solar Cycles 23 and 24. We use a comprehensive set of in-situ observations in
the near-Earth solar wind (Wind and ACE) and remove the periods when
large-scale interplanetary coronal mass ejections were present. The
investigated period features significant variations in the global coronal
structure, including the frequent presence of low-latitude active regions in
2006-2007, long-lived low- and mid-latitude coronal holes in 2006 - mid-2008
and mostly the quiet Sun in 2009. We examine both Carrington Rotation averages
of selected solar plasma, charge state and compositional parameters and
distributions of these parameters related to Quiet Sun, Active Region Sun and
the Coronal Hole Sun. While some of the investigated parameters (e.g., speed,
the C^{+6}/C^{+4} and He/H ratio) show clear variations over our study period
and with solar wind source type, some (Fe/O) exhibit very little changes. Our
results highlight the difficulty in distinguishing between the slow solar wind
sources based on the inspection of the solar wind conditions.Comment: 19 pages, 6 figures, 1 table, Solar Physics, in pres
Analysis of the substructure within a complex magnetic cloud on 3–4 September 2008
In this paper we have analyzed a substructure found within a leading part of
a north–south-oriented magnetic cloud (MC) observed on 3–4 September 2008 in
the near-Earth solar wind by multiple spacecraft (ACE, Wind, THEMIS B and C).
The MC was preceded by a stream interface (SI) and followed by a high-speed
stream (HSS). The identified substructure featured a strong depletion of
suprathermal halo electrons and showed distinct magnetic field and plasma
signatures. It occurred where suprathermal electron flow within a cloud
changed from bidirectional to unidirectional, indicating change in the field
line connectivity to the Sun. We found that the substructure maintained
roughly its integrity from the first Lagrangian point to the vicinity of the
Earth's bow shock in the front edge of the MC, but revealed small changes in
the structure which could be explained either by temporal evolution or
spatial configuration of the spacecraft