Modelling of sawtooth-induced fast ion transport in positive and negative triangularity in TCV

Internal kinks are a common magneto hydro-dynamic (MHD) instability observed in tokamak operation when the q profile in the plasma core is close to unity. This MHD instability impacts both the transport of the bulk plasma (current, particle and energy transport) and minority species, such as fast ions. In TCV (R 0 /a = 0.88 m/0.25 m) the fast ion population is generated in the plasma by neutral beam tangential injection of energies up to 28 keV. TCV features 16 active shaping coils permitting a great flexibility in plasma shape, including negative triangularity (δ) configurations that show surprisingly high confinement. This study focuses on the transport of fast ions induced by sawteeth, by comparing two triangularity cases and simulation results with experimental data. Comparison of two equilibria with opposite δ shows that the fast ion drifts are larger for δ < 0. Furthermore, the sawtooth-induced transport in this case is larger than δ > 0 in similar conditions. Comparison with experimental data confirms the dominance of the modification of thermal kinetic profiles following the sawtooth crash in explaining drops in the neutron rates and FIDA signals. Additional fast ion diffusion, however, improves the interpretation of the experimental data. For δ < 0, the amplitude of the perturbation better representing the experimental data is larger. Finaly, an exploratory study for 50 keV particles (soon available in TCV) shows that the situation does not worsen for such particles.

Steve: The optical signature of subauroral ion drifts

&lt;p&gt;Little is currently known about the optical phenomenon known as Steve. The first scientific publication on the subject suggests that Steve is associated with an intense subauroral ion drift (SAID). However, additional inquiry is warranted as this suggested relationship as it is based on a single case study. Here we present eight occurrences of Steve with coincident or near&amp;#8208;coincident measurements from the European Space Agency's Swarm satellites and show that Steve is consistently associated with SAID. When satellite observations coincident with Steve are compared to that of typical SAID, we find the SAID associated with Steve to have above average peak ion velocities and electron temperatures, as well as extremely low plasma densities.&lt;/p&gt;

Variations of Poynting Flux in the Northern Hemisphere during Quiet Times

&lt;p&gt;&lt;span&gt;Poynting flux energy is deposited from the magnetosphere in high latitudes, and measures the electromagnetic energy transmitted between the magnetosphere and the ionosphere. Little attention has been paid on the seasonal variation of the longitudinal pattern of the Poynting flux. Here, using long-term measurements of the ion drifts and the magnetic field by the DMSP satellite in the topside ionosphere, a statistical investigation of the longitudinal distributions of the Poynting flux in polar region during quiet times is conducted. Both case study and statistics show that there is a local maximum in downward Poynting flux in the pre-noon sector. Generally, the maximum is centered around geographic longitude of 120&amp;#176; west and geographic latitude of 80&amp;#176;, meaning that the total energy transferred into the ionosphere is the greatest in this region. The longitudinal distribution of the Poynting flux also exhibit clear seasonal variations with the longitudinal asymmetry the most significant in norther summer. The results could provide some new sights in future investigations of magnetosphere-ionosphere coupling in the polar region with observations and simulations.&lt;/span&gt;&lt;/p&gt;

FAST SUBAURORAL DRIFTS OF IONOSPHERE PLASMA ACCORDING TO DATA FROM YAKUT MERIDIONAL CHAIN OF STATIONS

Using long-term data from Yakut meridional chain of Yakutsk — Zhigansk — Batagay — Tixie ionospheric stations, we study ionospheric signatures of fast subauroral ion drift. Sharp drops or “falls” of critical frequencies (FCF) of the ionospheric F layer are shown to be one of the main signatures of the development of fast subauroral ion drifts near or at the zenith of the observation station. Comparison between long-term ground-based and satellite measurements indicates that there is good agreement between seasonal variation in the probability of occurrence of FCF derived from ground-based data and subauroral ion drifts derived from DMSP satellite data. Such a coincidence implies that both satellite and ground-based measurement methods register the same phenomenon in the boundary layers of the plasmasphere, namely, the appearance and development of electric fields of magnetospheric origin. The local time for recording of falls of the critical frequency derived from the ground-based data is shown to closely coincide with the appearance time of subauroral polarization streams of plasma according to satellite data. We can therefore conclude that most of the observed FCFs derived from ground-based data refer to intense storms.

FAST SUBAURORAL DRIFTS OF IONOSPHERE PLASMA ACCORDING TO DATA FROM YAKUT MERIDIONAL CHAIN OF STATIONS

Using long-term data from Yakut meridional chain of Yakutsk — Zhigansk — Batagay — Tixie ionospheric stations, we study ionospheric signatures of fast subauroral ion drift. Sharp drops or “falls” of critical frequencies (FCF) of the ionospheric F layer are shown to be one of the main signatures of the development of fast subauroral ion drifts near or at the zenith of the observation station. Comparison between long-term ground-based and satellite measurements indicates that there is good agreement between seasonal variation in the probability of occurrence of FCF derived from ground-based data and subauroral ion drifts derived from DMSP satellite data. Such a coincidence implies that both satellite and ground-based measurement methods register the same phenomenon in the boundary layers of the plasmasphere, namely, the appearance and development of electric fields of magnetospheric origin. The local time for recording of falls of the critical frequency derived from the ground-based data is shown to closely coincide with the appearance time of subauroral polarization streams of plasma according to satellite data. We can therefore conclude that most of the observed FCFs derived from ground-based data refer to intense storms.