09:45 〜 10:00
[PEM10-03] On the electron acceleration process as a carrier of field-aligned current and its energy conversion process in the Alfvén wavefront
キーワード：アルヴェーン波、電子加速、エネルギー変換過程
It is well known that the Alfven wave is an important media responsible for the transfer of FACs and momentum in the magnetosphere-ionosphere coupling. In the time scale of the MHD response, the FAC is generally represented as the shear component of the magnetic field with the magnetic field as the principal axis, and the associated current carriers are not discussed.
From the standpoint of the ion-electron two-fluid scheme, due to the difference in inertial forces acting on ions and electrons, the current perpendicular to the magnetic field is understood to be carried by the polarization drift of ions, while the FAC is carried by electrons.
At the Alfvén wavefront, the following electrodynamic response perpendicular to the magnetic field direction is generated. Since there is a velocity shear of ion polarization drift at the wavefront, an electric field shear is also generated, resulting in the induction of a magnetic field. The induced magnetic field shear generates an Ampere force, which accelerates the ions and eliminates the velocity shear of the polarization drift, causing the wavefront to move further along the magnetic field line, and after the wavefront passes, the magnetic field shear structure corresponding to the FAC and expected column-charge is formed along the magnetic field. The induced magnetic field shear generates an Ampere force, which accelerates the ions and eliminates the velocity shear of the polarization drift, causing the wavefront to move further along the magnetic field lines, and after passing through the wavefront, the FAC corresponding magnetic field shear structure and column charge are formed along the magnetic field.
So how do electrons gain velocity in the direction of the magnetic field to become carriers of the FAC? Since the acceleration process of electrons is not included in the above perpendicular electrodynamic response process, there will inevitably be a difference between the FAC density and the corresponding magnetic field shear, which is taken into account from the parallel velocity of electrons. This results in a displacement current, which leads to the growth of a parallel electric field. The parallel electric field thus created accelerates and decelerates the electrons, and as the difference between the electron parallel velocity and the FAC magnetic field shear is eliminated, the electrons have acquired the velocity in the direction of the magnetic field as carriers of the FAC. These responses occur on the time scale of plasma oscillations. In the present study, we focus on the energy conversion process in the acquisition of the FAC carrier velocity of electrons, and clarify that the twisting of the magnetic field shear created by the Alfven wave is resolved in this process and converted into the energy acquisition of electrons. In this presentation, we will introduce the basic process and its application.
From the standpoint of the ion-electron two-fluid scheme, due to the difference in inertial forces acting on ions and electrons, the current perpendicular to the magnetic field is understood to be carried by the polarization drift of ions, while the FAC is carried by electrons.
At the Alfvén wavefront, the following electrodynamic response perpendicular to the magnetic field direction is generated. Since there is a velocity shear of ion polarization drift at the wavefront, an electric field shear is also generated, resulting in the induction of a magnetic field. The induced magnetic field shear generates an Ampere force, which accelerates the ions and eliminates the velocity shear of the polarization drift, causing the wavefront to move further along the magnetic field line, and after the wavefront passes, the magnetic field shear structure corresponding to the FAC and expected column-charge is formed along the magnetic field. The induced magnetic field shear generates an Ampere force, which accelerates the ions and eliminates the velocity shear of the polarization drift, causing the wavefront to move further along the magnetic field lines, and after passing through the wavefront, the FAC corresponding magnetic field shear structure and column charge are formed along the magnetic field.
So how do electrons gain velocity in the direction of the magnetic field to become carriers of the FAC? Since the acceleration process of electrons is not included in the above perpendicular electrodynamic response process, there will inevitably be a difference between the FAC density and the corresponding magnetic field shear, which is taken into account from the parallel velocity of electrons. This results in a displacement current, which leads to the growth of a parallel electric field. The parallel electric field thus created accelerates and decelerates the electrons, and as the difference between the electron parallel velocity and the FAC magnetic field shear is eliminated, the electrons have acquired the velocity in the direction of the magnetic field as carriers of the FAC. These responses occur on the time scale of plasma oscillations. In the present study, we focus on the energy conversion process in the acquisition of the FAC carrier velocity of electrons, and clarify that the twisting of the magnetic field shear created by the Alfven wave is resolved in this process and converted into the energy acquisition of electrons. In this presentation, we will introduce the basic process and its application.