scholarly journals A numerical study of the interaction between two ejecta in the interplanetary medium: one- and two-dimensional hydrodynamic simulations

2004 ◽  
Vol 22 (10) ◽  
pp. 3741-3749 ◽  
Author(s):  
A. Gonzalez-Esparza ◽  
A. Santillán ◽  
J. Ferrer
Keyword(s):  
Hydrodynamic Model ◽  
Physical Mechanism ◽  
Interplanetary Medium ◽  
Numerical Study ◽  
Two Dimensions ◽  
Magnetic Clouds ◽  
The Sun ◽  
Two Dimensional ◽  
Hydrodynamic Simulations

Abstract. We studied the heliospheric evolution in one and two dimensions of the interaction between two ejecta-like disturbances beyond the critical point: a faster ejecta 2 overtaking a previously launched slower ejecta 1. The study is based on a hydrodynamic model using the ZEUS-3-D code. This model can be applied to those cases where the interaction occurs far away from the Sun and there is no merging (magnetic reconnection) between the two ejecta. The simulation shows that when the faster ejecta 2 overtakes ejecta 1 there is an interchange of momentum between the two ejecta, where the leading ejecta 1 accelerates and the tracking ejecta 2 decelerates. Both ejecta tend to arrive at 1AU having similar speeds, but with the front of ejecta 1 propagating faster than the front of ejecta 2. The momentum is transferred from ejecta 2 to ejecta 1 when the shock initially driven by ejecta 2 passes through ejecta 1. Eventually the two shock waves driven by the two ejecta merge together into a single stronger shock. The 2-D simulation shows that the evolution of the interaction can be very complex and there are very different signatures of the same event at different viewing angles; however, the transferring of momentum between the two ejecta follows the same physical mechanism described above. These results are in qualitative agreement with in-situ plasma observations of "multiple magnetic clouds" detected at 1AU.

scholarly journals Flux rope axis geometry of magnetic clouds deduced from in situ data

2013 ◽  
Vol 8 (S300) ◽  
pp. 265-268
Author(s):  
Miho Janvier ◽  
Pascal Démoulin ◽  
Sergio Dasso
Keyword(s):  
Interplanetary Medium ◽  
Magnetic Cloud ◽  
Flux Rope ◽  
Magnetic Clouds ◽  
Direct Integration ◽  
Axis Orientation ◽  
In Situ Data ◽  
Geometrical Features ◽  
Wide Range

AbstractMagnetic clouds (MCs) consist of flux ropes that are ejected from the low solar corona during eruptive flares. Following their ejection, they propagate in the interplanetary medium where they can be detected by in situ instruments and heliospheric imagers onboard spacecraft. Although in situ measurements give a wide range of data, these only depict the nature of the MC along the unidirectional trajectory crossing of a spacecraft. As such, direct 3D measurements of MC characteristics are impossible. From a statistical analysis of a wide range of MCs detected at 1 AU by the Wind spacecraft, we propose different methods to deduce the most probable magnetic cloud axis shape. These methods include the comparison of synthetic distributions with observed distributions of the axis orientation, as well as the direct integration of observed probability distribution to deduce the global MC axis shape. The overall shape given by those two methods is then compared with 2D heliospheric images of a propagating MC and we find similar geometrical features.

scholarly journals Configuration of a Magnetic Cloud From Solar Orbiter and Wind Spacecraft In-situ Measurements

2021 ◽  
Vol 9 ◽  
Author(s):  
Qiang Hu ◽  
Wen He ◽  
Lingling Zhao ◽  
Edward Lu
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Flux Rope ◽  
3D Models ◽  
Field Configuration ◽  
Magnetic Clouds ◽  
Physical Parameters ◽  
The Sun ◽  
Wind Spacecraft

Coronal mass ejections (CMEs) represent one type of the major eruption from the Sun. Their interplanetary counterparts, the interplanetary CMEs (ICMEs), are the direct manifestations of these structures when they propagate into the heliosphere and encounter one or more observing spacecraft. The ICMEs generally exhibit a set of distinctive signatures from the in-situ spacecraft measurements. A particular subset of ICMEs, the so-called Magnetic Clouds (MCs), is more uniquely defined and has been studied for decades, based on in-situ magnetic field and plasma measurements. By utilizing the latest multiple spacecraft measurements and analysis tools, we report a detailed study of the internal magnetic field configuration of an MC event observed by both the Solar Orbiter (SO) and Wind spacecraft in the solar wind near the Sun-Earth line. Both two-dimensional (2D) and three-dimensional (3D) models are applied to reveal the flux rope configurations of the MC. Various geometrical as well as physical parameters are derived and found to be similar within error estimates for the two methods. These results quantitatively characterize the coherent MC flux rope structure crossed by the two spacecraft along different paths. The implication for the radial evolution of this MC event is also discussed.

scholarly journals Evolutionary signatures in complex ejecta and their driven shocks

2004 ◽  
Vol 22 (10) ◽  
pp. 3679-3698 ◽  
Author(s):  
C. J. Farrugia ◽  
D. B. Berdichevsky
Keyword(s):  
Radial Distance ◽  
Magnetic Clouds ◽  
The Sun ◽  
Solar Cycles ◽  
Time Intervals ◽  
Form Complex ◽  
Event Sequences ◽  
Solar Observations ◽  
Halo Cmes

Abstract. We examine interplanetary signatures of ejecta-ejecta interactions. To this end, two time intervals of inner-heliospheric (≤1AU) observations separated by 2 solar cycles are chosen where ejecta/magnetic clouds are in the process of interacting to form complex ejecta. At the Sun, both intervals are characterized by many coronal mass ejections (CMEs) and flares. In each case, a complement of observations from various instruments on two spacecraft are examined in order to bring out the in-situ signatures of ejecta-ejecta interactions and their relation to solar observations. In the first interval (April 1979), data are shown from Helios-2 and ISEE-3, separated by ~0.33AU in radial distance and 28° in heliographic longitude. In the second interval (March-April 2001), data from the SOHO and Wind probes are combined, relating effects at the Sun and their manifestations at 1AU on one of Wind's distant prograde orbits. At ~0.67AU, Helios-2 observes two individual ejecta which have merged by the time they are observed at 1AU by ISEE-3. In March 2001, two distinct Halo CMEs (H-CMEs) are observed on SOHO on 28-29 March approaching each other with a relative speed of 500kms-1 within 30 solar radii. In order to isolate signatures of ejecta-ejecta interactions, the two event intervals are compared with expectations for pristine (isolated) ejecta near the last solar minimum, extensive observations on which were given by Berdichevsky et al. (2002). The observations from these two event sequences are then intercompared. In both event sequences, coalescence/merging was accompanied by the following signatures: heating of the plasma, acceleration of the leading ejecta and deceleration of the trailing ejecta, compressed field and plasma in the leading ejecta, disappearance of shocks and the strengthening of shocks driven by the accelerated ejecta. A search for reconnection signatures at the interface between the two ejecta in the March 2001 event was inconclusive because the measured changes in the plasma velocity tangential to the interface (Δνt) were not correlated with Δ(Bt /ρ). This was possibly due to lack of sufficient magnetic shear across the interface. The ejecta mergers altered interplanetary parameters considerably, leading to contrasting geoeffects despite broadly similar solar activity. The complex ejecta on 31 March 2001 caused a double-dip ring current enhancement, resulting in two great storms (Dst, corrected for the effect of magnetopause currents, <-450nT), while the merger on 5 April 1979 produced only a corrected Dst of ~-100nT, mainly due to effects of magnetopause currents.

scholarly journals Magnetic clouds seen at different locations in the heliosphere

2008 ◽  
Vol 26 (2) ◽  
pp. 213-229 ◽  
Author(s):  
L. Rodriguez ◽  
A. N. Zhukov ◽  
S. Dasso ◽  
C. H. Mandrini ◽  
H. Cremades ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Interplanetary Space ◽  
Field Configuration ◽  
Magnetic Clouds ◽  
Magnetic Characteristics ◽  
The Sun ◽  
Source Regions ◽  
Plasma Species ◽  
In Situ Observations

Abstract. We analyze two magnetic clouds (MCs) observed in different points of the heliosphere. The main aim of the present study is to provide a link between the different aspects of this phenomenon, starting with information on the origins of the MCs at the Sun and following by the analysis of in-situ observations at 1 AU and at Ulysses. The candidate source regions were identified in SOHO/EIT and SOHO/MDI observations. They were correlated with H-α images that were obtained from ground-based observatories. Hints on the internal magnetic field configuration of the associated coronal mass ejections are obtained from LASCO C2 images. In interplanetary space, magnetic and plasma moments of the distribution function of plasma species (ACE/Ulysses) were analyzed together with information on the plasma composition, and the results were compared between both spacecraft in order to understand how these structures interact and evolve in their cruise from the Sun to 5 AU. Additionally, estimates of global magnitudes of magnetic fluxes and helicity were obtained from magnetic field models applied to the data in interplanetary space. We have found that these magnetic characteristics were well kept from their solar source, up to 5 AU where Ulysses provided valuable information which, together with that obtained from ACE, can help to reinforce the correct matching of solar events and their interplanetary counterparts.

Spring Transition Period in Lake Ontario — A Numerical Study of the Causes of the Large Biological and Chemical Gradients

1980 ◽  
Vol 37 (5) ◽  
pp. 823-833 ◽  
Author(s):  
Donald Scavia ◽  
John R. Bennett
Keyword(s):  
Transition Period ◽  
Numerical Study ◽  
Vertical Mixing ◽  
Lake Ontario ◽  
Chemical Transformations ◽  
Two Dimensional ◽  
Offshore Structure ◽  
Chemical Gradients ◽  
Dimensional Models

A two-dimensional model that calculates physical transport, as well as in situ biological and chemical transformations, accurately simulates observations made along a north–south transect in Lake Ontario during April–June 1972. Simulation results show that, during the transition period between spring and summer, the inshore–offshore structure of biological and chemical distributions is controlled by the interaction of in situ processes and differences in vertical mixing on either side of the 4° isotherm. Owing to reversals in flow patterns, the effect of advection is to reduce concentration gradients, but the effect on overall distributions is minimal. An analysis of sinking losses in one- and two-dimensional models indicates that the artificially low sinking rates used in one-dimensional models of the Great Lakes result from the neglect of upwelling.Key words: Lake Ontario; model, hydrodynamic, ecological; sinking, upwelling, convection cells, chemical distributions

scholarly journals Magnetohydrodynamic convection in molten gallium

1999 ◽  
Vol 378 ◽  
pp. 97-118 ◽  
Author(s):  
A. JUEL ◽  
T. MULLIN ◽  
H. BEN HADID ◽  
D. HENRY
Keyword(s):  
Magnetic Field ◽  
Free Convection ◽  
Numerical Study ◽  
Two Dimensions ◽  
Main Flow ◽  
Temperature Gradients ◽  
Two Dimensional ◽  
Steady Magnetic Field ◽  
The Magnetic Field ◽  
Good Agreement

We present the results of an experimental and numerical study of the effects of a steady magnetic field on sidewall convection in molten gallium. The magnetic field is applied in a direction which is orthogonal to the main flow which reduces the convection and good agreement is found for the scaling of this effect with the relevant parameters. Moreover, qualitatively similar changes in the structure of the bulk of the flow are observed in the experiment and the numerical simulations. In particular, the flow is restricted to two dimensions by the magnetic field, but it remains different to that found in two-dimensional free convection calculations. We also show that oscillations found at even greater temperature gradients can be suppressed by the magnetic field.

MAGNETIC CLOUDS: A SUBJECT OF SPACE WEATHER PREDICTION

2005 ◽  
Vol 20 (29) ◽  
pp. 6650-6653
Author(s):  
A. GERANIOS ◽  
M. VANDAS ◽  
E. ANTONIADOU ◽  
O. ZACHAROPOULOU
Keyword(s):  
Space Weather ◽  
Coronal Mass Ejections ◽  
Strong Influence ◽  
Geomagnetic Storms ◽  
Interplanetary Medium ◽  
Weather Prediction ◽  
Magnetic Clouds ◽  
The Sun ◽  
Time Intervals ◽  
The Earth

Magnetic clouds are ideal objects for solar-terrestrial studies because of their simplicity and their extended time intervals of southward and northward magnetic fields. Magnetic clouds constitute a significant subset of coronal mass ejections with remarkable characteristics in the interplanetary medium and a strong influence on the Earth's magnetosphere, giving rise to geomagnetic storms. The evolution of such a cloud from the neighborhood of the Sun up to the Earth is numerically simulated for two cases, without and with a presence of a faster moving shock front. Its influence on the magnetosphere can be seen by the triggered geomagnetic storm. Therefore, magnetic clouds are an important subject for space weather predictions.

scholarly journals Reconstruction of the Parker spiral with the Reverse In situ data and MHD APproach - RIMAP

2020 ◽  
Author(s):  
Ruggero Biondo ◽  
Alessandro Bemporad ◽  
Andrea Mignone ◽  
Fabio Reale
Keyword(s):  
Interplanetary Medium ◽  
Small Scale ◽  
Reconstruction Technique ◽  
The Sun ◽  
Plasma Parameters ◽  
In Situ Data ◽  
Mhd Simulations ◽  
Solar Eruptions ◽  
In Situ Observations

The reconstruction of plasma parameters in the interplanetary medium is very important to understand the interplanetary propagation of solar eruptions and for Space Weather application purposes. Because only a few spacecraft are measuring in situ these parameters, reconstructions are currently performed by running complex numerical Magneto-hydrodynamic (MHD) simulations starting from remote sensing observations of the Sun. Current models apply full 3D MHD simulations of the corona or extrapolations of photospheric magnetic fields combined with and semiempirical relationships to derive the plasma parameters on a sphere centered on the Sun (inner boundary). The plasma is then propagated in the interplanetary medium up to the Earth’s orbit and beyond. Nevertheless, this approach requires significant theoretical and computational efforts, and the results are only in partial agreement with the in situ observations. In this paper we describe a new approach to this problem called RIMAP - Reverse In situ data and MHD APproach. The plasma parameters in the inner boundary at 0.1 AU are derived directly from the in situ measurements acquired at 1 AU, by applying a back reconstruction technique to remap them into the inner heliosphere. This remapping is done by using the Weber and Davies solar wind theoretical model to reconstruct the wind flowlines. The plasma is then re-propagated outward from 0.1 AU by running a MHD numerical simulation based on the PLUTO code. The interplanetary spiral reconstructions obtained with RIMAP are not only in a much better agreement with the in situ observations, but are also including many more small-scale longitudinal features in the plasma parameters that are not reproduced with the approaches developed so far.

scholarly journals Magnetic helicity content in solar wind flux ropes

2008 ◽  
Vol 4 (S257) ◽  
pp. 379-389 ◽  
Author(s):  
Sergio Dasso
Keyword(s):  
Solar Wind ◽  
Interplanetary Medium ◽  
Dynamical Evolution ◽  
Magnetic Clouds ◽  
Magnetic Helicity ◽  
Flux Tubes ◽  
Global Configuration ◽  
Flux Ropes ◽  
Field Lines

AbstractMagnetic helicity (H) is an ideal magnetohydrodynamical (MHD) invariant that quantifies the twist and linkage of magnetic field lines. In magnetofluids with low resistivity, H decays much less than the energy, and it is almost conserved during times shorter than the global diffusion timescale. The extended solar corona (i.e., the heliosphere) is one of the physical scenarios where H is expected to be conserved. The amount of H injected through the photospheric level can be reorganized in the corona, and finally ejected in flux ropes to the interplanetary medium. Thus, coronal mass ejections can appear as magnetic clouds (MCs), which are huge twisted flux tubes that transport large amounts of H through the solar wind. The content of H depends on the global configuration of the structure, then, one of the main difficulties to estimate it from single spacecraft in situ observations (one point - multiple times) is that a single spacecraft can only observe a linear (one dimensional) cut of the MC global structure. Another serious difficulty is the intrinsic mixing between its spatial shape and its time evolution that occurs during the observation period. However, using some simple assumptions supported by observations, the global shape of some MCs can be unveiled, and the associated H and magnetic fluxes (F) can be estimated. Different methods to quantify H and F from the analysis of in situ observations in MCs are presented in this review. Some of these methods consider a MC in expansion and going through possible magnetic reconnections with its environment. We conclude that H seems to be a ‘robust’ MHD quantity in MCs, in the sense that variations of H for a given MC deduced using different methods, are typically lower than changes of H when a different cloud is considered. Quantification of H and F lets us constrain models of coronal formation and ejection of flux ropes to the interplanetary medium, as well as of the dynamical evolution of MCs in the solar wind.

scholarly journals A comparison of bow shock models with Cluster observations during low Alfvén Mach number magnetic clouds

2013 ◽  
Vol 31 (6) ◽  
pp. 1011-1019 ◽  
Author(s):  
L. Turc ◽  
D. Fontaine ◽  
P. Savoini ◽  
H. Hietala ◽  
E. K. J. Kilpua
Keyword(s):  
Solar Wind ◽  
Mach Number ◽  
Interplanetary Medium ◽  
Normal Direction ◽  
Bow Shock ◽  
The Other ◽  
Magnetic Clouds ◽  
Shock Models ◽  
In Situ Observations

Abstract. Magnetic clouds (MCs) are very geoeffective solar wind structures. Their properties in the interplanetary medium have been extensively studied, yet little is known about their characteristics in the Earth's magnetosheath. The Cluster spacecraft offer the opportunity to observe MCs in the magnetosheath, but before MCs reach the magnetosphere, their structure is altered when they interact with the terrestrial bow shock (BS). The physics taking place at the BS strongly depends on ΘBn, the angle between the shock normal and the interplanetary magnetic field. However, in situ observations of the BS during an MC's crossing are seldom available. In order to relate magnetosheath observations to solar wind conditions, we need to rely on a model to determine the shock's position and normal direction. Yet during MCs, the models tend to be less accurate, because the Alfvén Mach number (MA) is often significantly lower than in regular solar wind. On the contrary, the models are generally optimised for high MA conditions. In this study, we compare the predictions of four widely used models available in the literature (Wu et al., 2000; Chapman and Cairns, 2003; Jeřáb et al., 2005; Měrka et al., 2005b) to Cluster's dayside BS crossings observed during five MC events. Our analysis shows that the ΘBn angle is well predicted by all four models. On the other hand, the Jeřáb et al. (2005) model yields the best estimates of the BS position during low MA MCs. The other models locate the BS either too far from or too close to Earth. The results of this paper can be directly used to estimate the BS parameters in all studies of MC interaction with Earth's magnetosphere.

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