Magnetosonic Shock Waves Research Articles

High-energy flare explosions driven by 3-dimensional X-type current loop coalescence

We present a model for high-energy solar flare explosions driven by 3-dimensional X-type current loop coalescence. The 3-dimensional X-type current loop coalescence, where two crossed flux-tubes interact at one point, is a fundamentally new process as compared to the 1-D and 2-D cases studied earlier. This process is studied by a first-order approach of the relevant variables near the point of coalescence; it appears to yield reliable information in a sufficiently large area around this point. It is shown that, following a strong plasma collapse due to the pinch effect, a point-like plasma explosion can be driven while fast magnetosonic shock waves can also be excited. We found that the conditions in the area producing the remarkable flare bursts of 21 May, 1984 were indeed such that the many flare spikes could have been due to 3-D explosive X-type current loop coalescence. We also show, by studying the conditions of shock formation in a gamma ray flare, that the time delay of γ-rays from the impulsive phase could be the time needed for the shock formation in the flaring region.

Prompt particle acceleration and plasma jet formation during current loop coalescence in solar flares

view Abstract Citations (24) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Prompt Particle Acceleration and Plasma Jet Formation during Current Loop Coalescence in Solar Flares Sakai, Jun-Ichi Abstract Numerical simulations based on the theory of Sakai and Tajima (1986) are used to study high-energy particle acceleration during current loop coalescence in solar flares. The results show that the electrons and protons can be quasi-periodically accelerated to relativistic energies in a very short period of time (much less than 1 sec) when the ratio of poloidal (loop current) to toroidal (potential field) components of the magnetic field is greater than one. It is shown that the spiral two-sided plasma jet can be explosively driven by the plasma rotational motion during the two-current loop coalescence process. Also, it is found that the rebound following the plasma collapse caused by the magnetic pinch effect may induce super-magnetosonic flow that can lead to fast magnetosonic shock waves. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1990 DOI: 10.1086/191468 Bibcode: 1990ApJS...73..321S Keywords: Coronal Loops; Particle Acceleration; Plasma Jets; Solar Flares; Magnetic Field Configurations; Magnetoelastic Waves; Relativistic Particles; Solar Electrons; Solar Magnetic Field; Solar Protons; Solar Physics; HYDROMAGNETICS; PARTICLE ACCELERATION; SUN: FLARES full text sources ADS |

Prompt simultaneous acceleration of protons and electrons to relativistic energies by shock waves in solar flares

view Abstract Citations (27) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Prompt Simultaneous Acceleration of Protons and Electrons to Relativistic Energies by Shock Waves in Solar Flares Ohsawa, Yukiharu ; Sakai, Jun-Ichi Abstract It is shown by theory and fully relativistic, electromagnetic particle simulation that a collisionless fast magnetosonic shock wave can promptly accelerate protons and electrons to relativistic energies; proton energies greater than about 10 to the 9th eV and electron energies greater than about 10 to the 6th eV. The time needed for the proton acceleration is of the order of the ion cyclotron period and is quite short (much less than 1 s for solar plasmas). The electron acceleration time is shorter than the ion cyclotron period. The present shock acceleration mechanism can explain important features of observed particle acceleration in the impulsive phase of solar flares; simultaneous and prompt acceleration of protons and electrons to relativistic energies. Publication: The Astrophysical Journal Pub Date: September 1988 DOI: 10.1086/166668 Bibcode: 1988ApJ...332..439O Keywords: Particle Acceleration; Relativistic Particles; Shock Waves; Solar Electrons; Solar Flares; Solar Protons; Collisionless Plasmas; Ion Cyclotron Radiation; Particle Energy; Solar Physics; PARTICLE ACCELERATION; SHOCK WAVES; SUN: FLARES full text sources ADS |

Plasma Heating by a Magnetosonic Shock Wave through Resonant Ion Acceleration

Resonant wave-particle interactions in magnetosonic shock waves are studied by theory and simulation. The number of ions trapped by a perpendicular laminar shock in a finite beta plasma is evaluated, and the amount of shock heating due to resonant ion acceleration is analytically obtained in terms of the Alfven Mach number and upstream plasma parameters. Some effects of trapped ions on shock waves are also discussed. In addition, it is shown that a laminar oblique shock can reflect some electrons by a magnetic mirror effect, in spite of a large positive potential in the shock region. These theoretical predictions are confirmed by a fully electromagnetic particle simulation with full ion and electron dynamics in one spatial dimension.

Particle acceleration by magnetic reconnection and shocks during current loop coalescence in solar flares

This article reviews recent development of the theory of current loop coalescence and shock waves, giving particular attention to particle acceleration caused by these processes. First, explosive reconnection driven by the current loop coalescence and associated particle acceleration are studied by theoretical and magnetohydrodynamic simulation methods and the results are compared with observations of solar flares; this model gives a good explanation for the quasi-periodic structure of some solar flare bursts. Next follows a discussion of particle acceleration in association with fast magnetosonic shock waves. It is shown theoretically and by relativistic particle simulation that a quasi-perpendicular shock wave can accelerate trapped ions in the direction perpendicular to the ambient magnetic field up to speeds much greater than the Alfven speed, $$\upsilon \sim \upsilon _A (m_i /m_e )^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}$$ . When the ambient magnetic field is rather strong (ω ce ≳ ω pe ), both ions and electrons can be accelerated to relativistic energies. For both the nonrelativistic and relativistic cases, the time needed for the acceleration is very short; it is $$t \sim \omega _{ci}^{ - 1} (m_i /m_e )^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}$$ for the ions. These results are compared with the rapid and simultaneous acceleration of ions and electrons in the impulsive phase of solar flares.

Prompt proton and electron acceleration to relativistic energies in solar flares

As a possible mechanism for particle acceleration in the impulsive phase of solar flares, a new particle acceleration mechanism in shock waves is proposed; a collisionless fast magnetosonic shock wave can promptly accelerate protons and electrons to relativistic energies, which was found by theory and relativistic particle simulation. The simultaneous acceleration of protons and electrons takes place in a rather strong magnetic field such that ωce ≳ ωpe. For a weak magnetic field (ωce ≪ ωpe), strong acceleration occurs to protons only. Resonant protons gain relativistic energies within the order of the ion cyclotron period (much less than 1 s for solar plasma parameters). The electron acceleration time is shorter than the ion-cyclotron period.

Relativistic Shock Wave

Perpendicular shock waves in rather strong magnetic fields (ω ce ≥ω pe ) are studied by a 1- 2/2 dimension (one dimension in real space and three dimension in velocity space), fully relativistic, fully electromagnetic particle simulation with full ion and electron dynamics. In that parameter regime relativistic effects become important in fast magnetosonic shock waves, even if the thermal speeds of ions and electrons in the upstream region are much smaller than the speed of light; a shock wave can trap some ions and promptly accelerate them to relativistic energies. Furthermore, with the mechanism different from that of ions, some electrons also gain relativistic energies through interactions with strong electric fields in the shock region. By showing various simulation results, we discuss the acceleration proccsses in detail.

Particle Reflection and Plasma Heating by a Laminar Magnetosonic Shock Wave

The fraction of ions trapped by a laminar magnetosonic shock wave is evaluated theoretically. The heating rate due to the resonant ion acceleration is then obtained interms of the Mach number and upstream plasma parameters. In addition, it is shown that, in spite of the large positive potential in the shock region, a laminar shock can reflect some electrons, as well as ions, because of the magnetic mirror effect.

Nonstochastic prompt proton acceleration by fast magnetosonic shocks in the solar plasma

Theoretical and numerical analyses are carried out for plasma heating and proton acceleration (V x B) due to magnetosonic shock waves (MSW) in the solar plasma. A simple model is developed for V x B acceleration by examining a single-particle orbit in a high-amplitude monochromatic electrostatic wave moving in a direction perpendicular to an external magnetic field. The particle can attain the E x B drift velocity. The model is used to derive the maximum velocity a particle can attain when driven by quasi-parallel and quasi-perpendicular MSW. Acceleration is found to be significantly stronger witn the latter, as is demonstrated with results of a 2.5 dimension simulation of acceleration by a quasi-perpendicular MSW. Implications of the results for modeling coronal heating and proton acceleration by MSWs produced by solar flares are discussed. 39 references.

Comment on “The adiabatic energy change of plasma electrons and the frame dependence of the cross‐shock potential at collisionless magnetosonic shock waves” By C. C. Goodrich and J. D. Scudder

Comment on “The adiabatic energy change of plasma electrons and the frame dependence of the cross‐shock potential at collisionless magnetosonic shock waves” By C. C. Goodrich and J. D. Scudder

Reply [ to “Comment on “Increase of ion kinetic temperature across a collisionless shock: I. A new concept by L. C. Lee et al.” and “Ion acceleration in quasiperpendicular magnetosonic shock waves with subcritical Mach number by Y. Ohsawa and J. Sakai””

Reply [ to “Comment on “Increase of ion kinetic temperature across a collisionless shock: I. A new concept by L. C. Lee et al.” and “Ion acceleration in quasiperpendicular magnetosonic shock waves with subcritical Mach number by Y. Ohsawa and J. Sakai””

Reply [to “Comment on ‘The adiabatic energy change of plasma electrons and the frame dependence of the cross‐shock potential at collisionless magnetosonic shock waves’ By C. C. Goodrich and J. D. Scudder”

Journal of Geophysical Research: Space PhysicsVolume 91, Issue A6 p. 7135-7136 Commentaries Reply [to “Comment on ‘The adiabatic energy change of plasma electrons and the frame dependence of the cross-shock potential at collisionless magnetosonic shock waves’ By C. C. Goodrich and J. D. Scudder”] C. C. Goodrich, C. C. GoodrichSearch for more papers by this authorJ. D. Scudder, J. D. ScudderSearch for more papers by this author C. C. Goodrich, C. C. GoodrichSearch for more papers by this authorJ. D. Scudder, J. D. ScudderSearch for more papers by this author First published: 1 June 1986 https://doi.org/10.1029/JA091iA06p07135Citations: 12AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume91, IssueA61 June 1986Pages 7135-7136 RelatedInformation

Reply [to ”Comment on “Increase of ion kinetic temperature across a collisionless shock: I. A new concept by L. C. Lee et al.” and “Ion acceleration in quasiperpendicular magnetosonic shock waves with subcritical Mach number by Y. Ohsawa and J. Sakai””

Reply [to ”Comment on “Increase of ion kinetic temperature across a collisionless shock: I. A new concept by L. C. Lee et al.” and “Ion acceleration in quasiperpendicular magnetosonic shock waves with subcritical Mach number by Y. Ohsawa and J. Sakai””

Comment on “Increase of Ion kinetic temperature across a collisionless shock: I. A new concept by L. C. Lee et al.” and “Ion acceleration in quasiperpendicular magnetosonic shock waves with subcritical Mach number by Y. Ohsawa and J. Sakai”

The question of ion heating at subcritical collisionless shocks is reviewed in light of newly proposed mechanisms.

Production of Highly Relativistic Ions and Electrons by Quasi-Perpendicular Magnetosonic Shock Waves

It is shown that a non-relativistic theory for laminar shocks breaks down for a plasma having a rather high Alfvén speed, \(v_{\text{A}}{\gtrsim}c\)( m e / m i ) 1/2 . By using a 2-1/2 dimension, fully relativistic, fully electromagnetic particle code, time evolution of quasi-perpendicular shocks in such plasmas is studied. Some ions and electrons are accelerated simultaneously to highly relativistic speeds by the shock.

Resonant ion acceleration by oblique magnetosonic shock wave in a collisionless plasma

A magnetosonic shock wave propagating obliquely to a magnetic field is studied by theory and simulation, with particular attention to the resonant ion acceleration (the vp×B acceleration) by the shock. Theoretical analysis based on a two-fluid model shows that, in the laminar shock, the electric field strength in the direction normal to the wave is about (mi/me)1/2 times larger for the quasiperpendicular shock than that for the quasiparallel shock, which is a reflection of the fact that the width of the quasiperpendicular shock is much smaller than that of the quasiparallel shock. Time evolution of a totally self-consistent magnetosonic shock wave is studied by using a 2 1/2 -dimensional fully relativistic, fully electromagnetic particle simulation with full ion and electron dynamics. Even the low Mach number shock wave can significantly accelerate some ions by the vp×B acceleration. The resonant ion acceleration occurs more strongly in the quasiperpendicular shock, because the magnitude of this acceleration is proportional to the electric field strength.

Ion acceleration in quasi‐perpendicular collisionless magnetosonic shock waves with subcritical Mach number

A self‐consistent evolution of quasi‐perpendicular collisionless laminar magnetosonic shock waves with subcritical Mach number is investigated by using a 2‐1/2 dimension, relativistic, electromagnetic particle code with full ion and electron dynamics. It is shown that significant ion acceleration occurs within the shock ramp by resonant interactions. The ions are heated primarily in the direction perpendicular to a magnetic field. Our results are in good agreement with the recent observations of interplanetary shocks by ISEE spacecraft.

Strong ion acceleration by a collisionless magnetosonic shock wave propagating perpendicularly to a magnetic field

A 2 1/2 -dimension, fully relativistic, fully electromagnetic particle code is used to study the time evolution of a nonlinear magnetosonic pulse propagating in a direction perpendicular to a magnetic field. The pulse is excited by an instantaneous piston acceleration, and evolves in a totally self-consistent manner. A large amplitude pulse traps some ions and accelerates them parallel to the wave front. They are detrapped when their velocities become of the order of the sum of the E×B drift velocity and the wave phase velocity, where E is the electric field in the direction of the wave propagation. The pulse develops into a quasishock wave in a collisionless plasma because of dissipation caused by the resonant ion acceleration. A simple nonlinear wave theory for a cold plasma describes the shock properties observed in the simulation except for the effects of resonant ions. In particular, the magnitude of an electric potential across the shock region is derived analytically and is found to be in good agreement with our simulations. The potential jump is proportional to B2, and hence the E×B drift velocity of the trapped ions is proportional to B.

Resonant Ion Acceleration by Collisionless Magnetosonic Shock Wave Propagating Obliquely to a Magnetic Field

A 2–1/2 dimensional relativistic electromagnetic particle code is used to study a time evolution of a selfconsistent nonlinear magnetosonic pulse propagating obliquely to a magnetic field. It is shown that the shock wave traps some ions and resonantly accelerates them parallel to the wave front. This acceleration is most efficient when the propagation angle is in the region \(\theta_{c}{\lesssim}\theta{\leqq}\pi/2\), where θ c = arctan (( m i / m e ) 1/2 -( m e / m i ) 1/2 ).

The adiabatic energy change of plasma electrons and the frame dependence of the cross‐shock potential at collisionless magnetosonic shock waves

In collisionless magnetosonic shock waves, ions are commonly thought to be decelerated by a dc electrostatic cross‐shock electric field along the shock normal , where γ is the effective polytrope index for electrons. By observation this ratio is ∼1/10 at the earth’s bow shock. When viewed in the de Hoffman‐Teller frame, corresponding changes in the ion kinematics occur. Since the e[ϕ*HT] is an order of magnitude smaller than the ion energy, the ions are not significantly affected by the electrostatic force. They are instead primarily retarded in this frame by the magnetic force. Since this latter force is proportional to the component of B out of the coplanarity plane, infinitesimally thin shock models may not be realistic for the study of the ion and electron dynamics in the de Hoffman‐Teller frame.