scholarly journals First simultaneous measurements of waves generated at the bow shock in the solar wind, the magnetosphere and on the ground

2009 ◽  
Vol 27 (1) ◽  
pp. 357-371 ◽  
Author(s):  
L. B. N. Clausen ◽  
T. K. Yeoman ◽  
R. C. Fear ◽  
R. Behlke ◽  
E. A. Lucek ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Cone Angle ◽  
Bow Shock ◽  
Wave Power ◽  
Sudden Increase ◽  
Model Predictions ◽  
Field Lines ◽  
Upstream Waves ◽  
The Imf

Abstract. On 5 September 2002 the Geotail satellite observed the cone angle of the Interplanetary Magnetic Field (IMF) change to values below 30° during a 56 min interval between 18:14 and 19:10 UT. This triggered the generation of upstream waves at the bow shock, 13 RE downstream of the position of Geotail. Upstream generated waves were subsequently observed by Geotail between 18:30 and 18:48 UT, during times the IMF cone angle dropped below values of 10°. At 18:24 UT all four Cluster satellites simultaneously observed a sudden increase in wave power in all three magnetic field components, independent of their position in the dayside magnetosphere. We show that the 10 min delay between the change in IMF direction as observed by Geotail and the increase in wave power observed by Cluster is consistent with the propagation of the IMF change from the Geotail position to the bow shock and the propagation of the generated waves through the bow shock, magnetosheath and magnetosphere towards the position of the Cluster satellites. We go on to show that the wave power recorded by the Cluster satellites in the component containing the poloidal and compressional pulsations was broadband and unstructured; the power in the component containing toroidal oscillations was structured and shows the existence of multi-harmonic Alfvénic continuum waves on field lines. Model predictions of these frequencies fit well with the observations. An increase in wave power associated with the change in IMF direction was also registered by ground based magnetometers which were magnetically conjunct with the Cluster satellites during the event. To the best of our knowledge we present the first simultaneous observations of waves created by backstreaming ions at the bow shock in the solar wind, the dayside magnetosphere and on the ground.

scholarly journals The statistics of foreshock cavities: results of a Cluster survey

2008 ◽  
Vol 26 (12) ◽  
pp. 3653-3667 ◽  
Author(s):  
L. Billingham ◽  
S. J. Schwartz ◽  
D. G. Sibeck
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Cone Angle ◽  
Solar Wind Plasma ◽  
Bow Shock ◽  
Systematic Change ◽  
Ion Density ◽  
Field Lines ◽  
Moderate Magnetic Field ◽  
Suprathermal Ions

Abstract. We use Cluster magnetic field, thermal ion, and energetic particle observations upstream of the Earth's bow shock to investigate the occurrence patterns of foreshock cavities. Such cavities are thought to form when bundles of magnetic field connect to the quasi-parallel bow shock. Shock-processed suprathermal ions can then stream along the field, back against the flow of the solar wind. These suprathermals enhance the pressure on shock-connected field lines causing them to expand into the surrounding ambient solar wind plasma. Foreshock cavities exhibit depressions in magnetic field magnitude and thermal ion density, associated with enhanced fluxes of energetic ions. We find typical cavity duration to be few minutes with interior densities and magnetic field magnitudes dropping to ~60% of those in the surrounding solar wind. Cavities are found to occur preferentially in fast, moderate magnetic field strength solar wind streams. Cavities are observed in all parts of the Cluster orbit upstream of the bow shock. When localised in a coordinate system organised by the underlying physical processes in the foreshock, there is a systematic change in foreshock cavity location with IMF cone angle. At low (high) cone angles foreshock cavities are observed outside (inside) the expected upstream boundary of the intermediate ion foreshock.

scholarly journals Venus's induced magnetosphere during active solar wind conditions at BepiColombo's Venus 1 flyby

2021 ◽  
Author(s):  
Martin Volwerk ◽  
Beatriz Sánchez-Cano ◽  
Daniel Heyner ◽  
Sae Aizawa ◽  
Nicolas André ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Interplanetary Magnetic Field ◽  
Bow Shock ◽  
Gravity Assist ◽  
Highly Active ◽  
Field Lines ◽  
Mass Ejection ◽  
The Magnetic Field

Abstract. Out of the two Venus flybys that BepiColombo uses as a gravity assist manoeuvre to finally arrive at Mercury, the first took place on 15 October 2020. After passing the bow shock, the spacecraft travelled along the induced magnetotail, crossing it mainly in the YVSO-direction. In this paper, the BepiColombo Mercury Planetary Orbiter Magnetometer (MPO-MAG) data are discussed, with support from three other plasma instruments: the Planetary Ion Camera (PICAM), the Mercury Electron Analyser (MEA) and the radiation monitor (BERM). Behind the bow shock crossing, the magnetic field showed a draping pattern consistent with field lines connected to the interplanetary magnetic field wrapping around the planet. This flyby showed a highly active magnetotail, with, e.g., strong flapping motions at a period of ~7 min. This activity was driven by solar wind conditions. Just before this flyby, Venus's induced magnetosphere was impacted by a stealth coronal mass ejection, of which the trailing side was still interacting with it during the flyby. This flyby is a unique opportunity to study the full length and structure of the induced magnetotail of Venus, indicating that the tail was most likely still present at about 48 Venus radii.

scholarly journals Jets in the Magnetosheath: IMF Control of Where They Occur

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.

scholarly journals Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations

2020 ◽  
Author(s):  
Lucile Turc ◽  
Vertti Tarvus ◽  
Andrew Dimmock ◽  
Markus Battarbee ◽  
Urs Ganse ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Mach Number ◽  
Field Strength ◽  
Flow Velocity ◽  
Magnetic Field Strength ◽  
Bow Shock ◽  
Wide Range ◽  
The Magnetic Field ◽  
The Imf

<p>The magnetosheath is the region bounded by the bow shock and the magnetopause which is home to shocked solar wind plasma. At the interface between the solar wind and the magnetosphere, the magnetosheath plays a key role in the coupling between these two media. Previous works have revealed pronounced dawn-dusk asymmetries in the magnetosheath properties, with for example the magnetic field strength and flow velocity being larger on the dusk side, while the plasma is denser, hotter and more turbulent on the dawn side. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker-spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions that have been processed to obtain the average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density and the flow velocity. We find that the Vlasiator model reproduces accurately the polarity of the asymmetries, but that their level tends to be higher than in spacecraft measurements, probably due to the different processing methods. We investigate how the asymmetries change when the IMF becomes more radial and when the Alfvén Mach number decreases. When the IMF makes a 30° angle with the Sun-Earth line instead of 45°, we find a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfvén Mach number leads to a decrease of the magnetic field asymmetry level and of the variability of the magnetosheath density and velocity, likely due to weaker foreshock processes.</p>

scholarly journals Jets in the magnetosheath: IMF control of where they occur

2019 ◽  
Vol 37 (4) ◽  
pp. 689-697 ◽  
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.

scholarly journals Venus's induced magnetosphere during active solar wind conditions at BepiColombo's Venus 1 flyby

2021 ◽  
Vol 39 (5) ◽  
pp. 811-831
Author(s):  
Martin Volwerk ◽  
Beatriz Sánchez-Cano ◽  
Daniel Heyner ◽  
Sae Aizawa ◽  
Nicolas André ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Interplanetary Magnetic Field ◽  
Bow Shock ◽  
Gravity Assist ◽  
Highly Active ◽  
Field Lines ◽  
Mass Ejection ◽  
The Magnetic Field

Abstract. Out of the two Venus flybys that BepiColombo uses as a gravity assist manoeuvre to finally arrive at Mercury, the first took place on 15 October 2020. After passing the bow shock, the spacecraft travelled along the induced magnetotail, crossing it mainly in the YVSO direction. In this paper, the BepiColombo Mercury Planetary Orbiter Magnetometer (MPO-MAG) data are discussed, with support from three other plasma instruments: the Planetary Ion Camera (SERENA-PICAM) of the SERENA suite, the Mercury Electron Analyser (MEA), and the BepiColombo Radiation Monitor (BERM). Behind the bow shock crossing, the magnetic field showed a draping pattern consistent with field lines connected to the interplanetary magnetic field wrapping around the planet. This flyby showed a highly active magnetotail, with e.g. strong flapping motions at a period of ∼7 min. This activity was driven by solar wind conditions. Just before this flyby, Venus's induced magnetosphere was impacted by a stealth coronal mass ejection, of which the trailing side was still interacting with it during the flyby. This flyby is a unique opportunity to study the full length and structure of the induced magnetotail of Venus, indicating that the tail was most likely still present at about 48 Venus radii.

Venus’s induced magnetosphere during active solar wind conditionsat BepiColombo’s Venus 1 flyby

2021 ◽  
Author(s):  
Martin Volwerk ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Interplanetary Magnetic Field ◽  
Bow Shock ◽  
Gravity Assist ◽  
Highly Active ◽  
Field Lines ◽  
Mass Ejection ◽  
The Magnetic Field

<p>Out of the two Venus flybys that BepiColombo uses as a gravity assist manoeuvre to finally arrive at Mercury, the first took place on 15 October 2020. After passing the bow shock, the spacecraft travelled along the induced magnetotail, crossing it mainly in the Y<sub>VSO</sub>-direction. We discuss the BepiColombo Mercury Planetary Orbiter Magnetometer (MPOMAG)<br />data, with support from three other plasma instruments: the Planetary Ion Camera (PICAM), the Mercury<br />Electron Analyser (MEA) and the radiation monitor (BERM). Behind the bow shock crossing, the magnetic field showed a<br />draping pattern consistent with field lines connected to the interplanetary magnetic field wrapping around the planet. This flyby showed a highly active magnetotail, with, e.g., strong flapping motions at a period of ~7 min. This activity was driven by solar wind conditions. Just before this flyby, Venus’s induced magnetosphere was impacted by a stealth coronal mass ejection, of which the trailing side was still interacting with it during the flyby. This flyby is a unique opportunity to study the full length and structure of the induced magnetotail of Venus, indicating that the tail was most likely still present at about 48 Venus radii. This presentation will take place after the second Venus flyby by Solar Orbiter and BepiColombo and Solar Orbiter on 9 and 10 August, respectively.</p>

Foreshock wave transmission into the magnetosheath and magnetosphere: results from global hybrid-Vlasov simulations

2021 ◽  
Author(s):  
Lucile Turc ◽  
Markus Battarbee ◽  
Urs Ganse ◽  
Andreas Johlander ◽  
Yann Pfau-Kempf ◽  
...  
Keyword(s):  
Solar Wind ◽  
Mach Number ◽  
Cone Angle ◽  
Low Frequency ◽  
Compressional Wave ◽  
Wave Transmission ◽  
Wave Power ◽  
Solar Wind Flow ◽  
Magnetic Pulsations ◽  
Wave Properties

<p>The foreshock, extending upstream of the quasi-parallel shock and populated with shock-reflected particles, is home to intense wave activity in the ultra-low frequency range.<em> </em>The most commonly observed of these waves are the “30 s” waves, fast magnetosonic waves propagating sunward in the plasma rest frame, but carried earthward by the faster solar wind flow. These waves are thought to be the main source of Pc3 magnetic pulsations (10 – 45 s) in the dayside magnetosphere. A handful of case studies with suitable spacecraft conjunctions have allowed simultaneous investigations of the wave properties in different geophysical regions, but the global picture of the wave transmission from the foreshock through the magnetosheath into the magnetosphere is still not known. In this work, we use global simulations performed with the hybrid-Vlasov model Vlasiator to study the Pc3 wave properties in the foreshock, magnetosheath and magnetosphere for different solar wind conditions. We find that in all three regions the wave power peaks at higher frequencies when the interplanetary magnetic field strength is larger, consistent with previous studies. While the transverse wave power decreases with decreasing Alfvén Mach number in the foreshock, the compressional wave power shows little variation. In contrast, in the magnetosheath and the magnetosphere, the compressional wave power decreases with decreasing Mach number. Inside the magnetosphere, the distribution of wave power varies with the IMF cone angle. We discuss the implications of these results for the propagation of foreshock waves across the different geophysical regions, and in particular their transmission through the bow shock.</p>

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