8 research outputs found
Electron inflow velocities and reconnection rates at earth's magnetopause and magnetosheath
Electron inflow and outflow velocities during magnetic reconnection at and near the dayside magnetopause are measured using satellites from NASA's Magnetospheric Multiscale (MMS) mission. A case study is examined in detail, and three other events with similar behavior are shown, with one of them being a recently published electron-only reconnection event in the magnetosheath. The measured inflow speeds of 200â400 km/s imply dimensionless reconnection rates of 0.05â0.25 when normalized to the relevant electron AlfvĂ©n speed, which are within the range of expectations. The outflow speeds are about 1.5â3 times the inflow speeds, which is consistent with theoretical predictions of the aspect ratio of the inner electron diffusion region. A reconnection rate of 0.04 ± 25% was obtained for the case study event using the reconnection electric field as compared to the 0.12 ± 20% rate determined from the inflow velocity.publishedVersio
Wave generation and energetic electron scattering in solar flares
We conduct two-dimensional particle-in-cell simulations to investigate the
scattering of electron heat flux by self-generated oblique electromagnetic
waves. The heat flux is modeled as a bi-kappa distribution with a T_parallel >
T_perp temperature anisotropy maintained by continuous injection at the
boundaries. The anisotropic distribution excites oblique whistler waves and
filamentary-like Weibel instabilities. Electron velocity distributions taken
after the system has reached a steady state show that these in stabilities
inhibit the heat flux and drive the total distributions towards isotropy.
Electron trajectories in velocity space show a circular-like diffusion along
constant energy surfaces in the wave frame. The key parameter controlling the
scattering rate is the average speed, or drift speed vd, of the heat flux
compared with the electron Alfven speed vAe, with higher drift speeds producing
stronger fluctua tions and a more significant reduction of the heat flux.
Reducing the density of the electrons carrying the heat flux by 50% does not
significantly affect the scattering rate. A scaling law for the electron
scattering rate versus vd/vAe is deduced from the simulations. The implications
of these results for understanding energetic electron transport during solar
flare energy release are discussed
Electron inflow velocities and reconnection rates at earth's magnetopause and magnetosheath
Electron inflow and outflow velocities during magnetic reconnection at and near the dayside magnetopause are measured using satellites from NASA's Magnetospheric Multiscale (MMS) mission. A case study is examined in detail, and three other events with similar behavior are shown, with one of them being a recently published electron-only reconnection event in the magnetosheath. The measured inflow speeds of 200â400 km/s imply dimensionless reconnection rates of 0.05â0.25 when normalized to the relevant electron AlfvĂ©n speed, which are within the range of expectations. The outflow speeds are about 1.5â3 times the inflow speeds, which is consistent with theoretical predictions of the aspect ratio of the inner electron diffusion region. A reconnection rate of 0.04 ± 25% was obtained for the case study event using the reconnection electric field as compared to the 0.12 ± 20% rate determined from the inflow velocity
Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere
This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere