Connecting interplanetary coronal mass ejections ICMEs to their solar pre-eruption source requires a clear understanding of how that source may have evolved during eruption. Gibson and Fan a have presented a three-dimensional numerical magnetohydrodynamic simulation of a CME, which showed how, in the course of eruption, a coronal flux rope may writhe and reconnect both internally and with surrounding fields in a manner that leads to a partial ejection of only part of the rope as a CME.

In this paper, we will explicitly describe how the evolution during eruption found in that simulation leads to alterations of the magnetic connectivity, helicity, orientation, and topology of the ejected portion of the rope so that it differs significantly from that of the pre-eruption rope.

Moreover, because a significant part of the magnetic helicity remains behind in the lower portion of the rope that survives the eruption, the region is likely to experience further eruptions. These changes would complicate how ICMEs embedded in the solar wind relate to their solar source. In particular, the location and evolution of transient coronal holes, topology of magnetic clouds "tethered spheromak"and likelihood of interacting ICMEs would differ significantly from what would be predicted for a CME which did not undergo writhing and partial ejection during eruption.

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magnetic helicity content in solar wind flux ropes

Simple search. Search terms. Gibson, S. Partially ejected flux ropes: Implications for interplanetary coronal mass ejections. Download PDF. Abstract Connecting interplanetary coronal mass ejections ICMEs to their solar pre-eruption source requires a clear understanding of how that source may have evolved during eruption.

In collections Journal Articles. Author s Sarah E. Copyright American Geophysical Union.

magnetic helicity content in solar wind flux ropes

Powered by Drupal.Pipin 1A. Pevtsov 2Yang Liu 3 and A. Kosovichev 4. Magnetic helicity conservation is believed to be rather significant for the nonlinear stage of the large-scale dynamo in solar-type stars. Figure 1 is a sketch of the general idea of how the magnetic helicity interplays with the dynamo processes in the stellar convection zone. It illustrates two basic theoretical ideas about the magnetic helicity in the solar dynamo. First, it shows the hemispheric magnetic helicity rule; and second, it shows that helicity of the global and local magnetic field of the Sun should have, in general, opposite signs.

Figure 1 Significance of magnetic helicity for solar-type dynamos 1. Panels a and b show the linear stages of the dynamo process. Panels c and d show how the magnetic helicity conservation affects the stage a because the global writhe is accompanied by the local twist of the global magnetic field in the flux-tube cross-section plane, and the direction of twist is opposite to the writhe. Directions of writhe and twist, which are shown in panel ehave opposite signs in the northern and southern hemispheres of the Sun.

Magnetic helicity is an integral measure of topological properties of the magnetic field in a closed volume, where is the magnetic vector potential,and is confined to the volume. Therefore, in general, to study magnetic helicity, we need the volume magnetic field distributions. The is the magnetic helicity density.

magnetic helicity content in solar wind flux ropes

The spatially or temporarily averaged characterizes the mean magnetic helicity or the mean linkage of the magnetic field in the domain of averaging 3. This quantity perfectly suits for comparison of the observational data with results of theoretical dynamo models. We decompose the magnetic field and its vector-potential into the mean and fluctuating parts:, where the small letters represent the small-scale fluctuations and the capital ones with over-bars are the large-scale fields.

In the case of solar magnetism, the time scale of mean magnetic field corresponds to the solar cycle period and small-scale magnetic field varies on much shorter intervals corresponding to the typical time scales of solar active regions. The solar dynamo predominantly operates in an axisymmetric dynamo regime. Therefore, we can express the relationship between the magnetic helicity density of the large- and small-scale magnetic fields as follows: Thus, the small-scale magnetic helicity densityincludes magnetic fields from all range of scales except the axisymmetric magnetic field.

To determine the magnetic helicity density, we employ a decomposition of the vector magnetic field into toroidal and poloidal components using scalar potentials and :. Calculations were done in the spectral space using the spherical harmonic decomposition.

Figure 2 illustrates reconstruction of vector magnetic potential for the Carrington rotation CR The large active region in the southern hemisphere produced the negative magnetic helicity density. It is opposite to the hemispheric helicity rule. Nearby the ARs of the same helicity sign occupy the big portion of solar surface on both sides of the solar equator. Figure 3 shows the time-latitude diagrams of the magnetic helicity density of the large-scale field, and the small-scale non-axisymmetric magnetic field.

Both the large- and small-scale magnetic fields of the Sun show the hemispheric helicity rule. Generally, evolution of in Cycle 24 agrees with results of Ref [5] for the current helicity of solar active regions in cycle In our data we see that the magnetic helicity density of the large- and small-scale fields often show the same sign in each hemisphere.

This may be due to the asymmetric development about the equator in Solar Cycle This results in the equatorial parity breaking in the large-scale magnetic field and vector potential components.

Please see a more detailed discussion in the paper 4. The hemispheric helicity rule and bi-helical distributions of the solar magnetic fields are essential properties of the solar dynamo operating in the convection zone. We find that in Solar Cycle 24 these properties of solar dynamo show a complicated evolution in the way which is not expected in any current dynamo models.

The suggested method of the magnetic helicity reconstruction can be applied to other stars where the low-degree modes of the vector magnetic field distributions can be used to calculate the magnetic vector potential and magnetic helicity density of the large-scale stellar magnetic field. References: [1] Blackman, E. Your email address will not be published. Contributed by V.Magnetic flux ropes MFRs are usually considered to be the magnetic structure that dominates the transport of helicity from the Sun into the heliosphere.

They entrain a confined plasma within a helically organized magnetic structure and are able to cause geomagnetic activity. The formation, evolution, and twist distribution of MFRs are issues subject to strong debate. Although different twist profiles have been suggested so far, none of them has been thoroughly explored yet.

Origin and structures of solar eruptions I: Magnetic flux rope

The aim of this work is to present a theoretical study of the conditions under which MFRs with different twist profiles are kink stable and thereby shed some light on the aforementioned aspects. The results are discussed in relation to MFR rotations, magnetic forces, the reversed chirality scenario, and the expansion throughout the heliosphere, among others, providing a theoretical background to improve the current understanding of the internal magnetic configuration of coronal mass ejections CMEs.

The data obtained by new missions like Parker Solar Probe or Solar Orbiter will give the opportunity to explore these results and ideas by observing MFRs closer than ever to the Sun.

This is a preview of subscription content, log in to check access. Rent this article via DeepDyve. Amari, T. Boundary motion-driven evolution. Antiochos, S. Archontis, V. Aulanier, G. Strong-to-weak shear transition in post-flare loops. Balmaceda, L. Cyr, O. Implications for self-similar evolution. Solar Phys. Bateman, G. Google Scholar.

Bennett, K. Berdichevsky, D. E 67 Bernstein, I. London Ser. A, Math. Brent, R.

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Burlaga, L. Cabello, I. Chiappinelli, R. Symmetry 11 7 Cho, K. Cremades, H. Dasso, S. Dungey, J. Einaudi, G. In: Physics of Magnetic Flux Ropes.Coronal mass ejections CMEs and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space.

The travel time of a CME to 1 AU is about 1—3 days, while energetic particles from the eruptions arrive even earlier. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.

Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Finally, we come to some conclusions and put forward some prospects in the future. This is a preview of subscription content, log in to check access.

Rent this article via DeepDyve. Characterizing and predicting the magnetic environment leading to solar eruptions. Nature, — Three-dimensional solutions of magnetohydrodynamic equationsfor prominence magnetic support: Twisted magnetic flux rope.

Astrophys J, L57—L A twisted flux rope model for coronal mass ejections and two-ribbon flares. Astrophys J, L49—L Coronal mass ejection: initiation, magnetic helicity, and flux ropes. Boundary motion-driven evolution. Astrophys J, — Google Scholar. Turbulent diffusion-driven evolution. Coronal mass ejection initiation: On the nature of the flux cancellation model.

Astrophys J, L26—L Coronal mass ejection initiation by converging photospheric flows: Toward a realistic model. Astrophys J, L The magnetic field of solar prominences. Astrophys J, L41—L A model for solar coronal mass ejections. Archontis V, Hood A W. Formation of Ellerman bombs due to 3D flux emergence. Astron Astrophys, — Eruption of magnetic flux ropes during flux emergence. Astron Astrophys, L35—L On the structure and evolution of complexity in sigmoids: A flux emergence model.The helicity of a smooth vector field defined on a domain in 3D space is the standard measure of the extent to which the field lines wrap and coil around one another.

It is a generalization of the topological concept of linking number to the differential quantities required to describe the magnetic field. As with many quantities in electromagnetism, magnetic helicity which describes magnetic field lines is closely related to fluid mechanical helicity which describes fluid flow lines. If magnetic field lines follow the strands of a twisted ropethis configuration would have nonzero magnetic helicity; left-handed ropes would have negative values and right-handed ropes would have positive values.

It is a conserved quantity in ideal magnetohydrodynamics zero resistivityand still remains conserved in a good approximation even with a small but finite resistivity, in which case magnetic reconnection dissipates energy.

However, for perfectly conducting boundaries or periodic systems without a net magnetic flux, the magnetic helicity is gauge invariant. A gauge-invariant relative helicity has been defined for volumes with non-zero magnetic flux on their boundary surfaces. From Wikipedia, the free encyclopedia. Influence of geometry and topology on helicity[J]. Magnetic Helicity in Space and Laboratory Plasmas Bibcode : SchpJ Space Science Reviews.

Bibcode : SSRv. Plasma Physics and Controlled Fusion. Bibcode : PPCF The Astrophysical Journal Letters. Bibcode : ApJ Categories : Physical quantities Plasma physics Astrophysics. Hidden categories: Wikipedia articles needing clarification from February All articles with unsourced statements Articles with unsourced statements from February Namespaces Article Talk.

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Solar Wind - Magnetosphere Coupling

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