Oct. 4, 2019

3:30 p.m. - 5 p.m.
6704 Geology

Presented By: Jeffrey Robertson,
UCLA

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Propagation of Alfven Waves in a Two Ion Species Plasma

Understanding the behavior of plasma waves in mixed-species plasmas is important for explaining many observations seen in both space and laboratory plasmas. The addition of a second ion species in a magnetized plasma introduces new behavior in the propagation of waves in the ion cyclotron region, such as the ion-ion hybrid cutoff frequency for parallel propagating shear Alfven waves [1]. Previous experiments on the Large Plasma Device (LAPD) have demonstrated the existence of a propagation gap for shear waves between the ion cyclotron frequencies of the two ion species [2], while more recent work has expanded the range of plasma conditions in which this was observed. Additionally, the ion-ion hybrid cutoff is documented for various mix ratios in order to determine its viability as a diagnostic for the ratio of ion densities. `

Oct. 11, 2019

3:30 p.m. - 5 p.m.
6704 Geology

Presented By: Yangyang Shen,
University of Calgary

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Microphysics of ion and electron energization in the topside ionosphere: Results from CASSIOPE/e-POP

Ionospheric ion (mainly O+) and electron energization and field-aligned transport are critical processes of magnetosphere-ionosphere-thermosphere coupling. The Canadian Enhanced Polar Outflow Probe (e-POP) satellite carries particle and field instruments specifically designed to study micro-scale characteristics of ion energization and outflow processes in the topside (325-1,500 km) ionosphere. The Suprathermal Electron/Ion Imager (SEI) instrument onboard e-POP has the capability of resolving two-dimensional low-energy (from sub-eV to 325 eV) particle distributions at time scales of up to 10 ms, or spatial scales of less than 100 m. This talk aims to present several discoveries resulting from direct measurements of particles and waves from e-POP. In particular, we will focus on observations and test particle simulations of transverse O+ ion heating from broadband extremely low frequency (BBELF) waves in the collisional ionosphere. We will also show the first direct observations of suprathermal (tens to hundreds of eV) electron acceleration perpendicular to the magnetic field in the topside ionosphere.

Oct. 18, 2019

3:30 p.m. - 5 p.m.
6704 Geology

Presented By: Vlacheslav Pilipenko,
Institute of Physics of the Earth, Moscow, Russia

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Fine structure of substorm and geomagnetically induced currents

The rapid changes of magnetic fields, that is high dB/dt, associated with substorms can excite large geomagnetically-induced currents (GICs) that can have harmful effects on technological systems. We have analyzed the characteristics of the dB/dt enhancements observed in Fennoscandia in 2015 using data from the magnetometer array IMAGE, covering a range of magnetic latitudes from 68° to 78°. The abrupt magnetic field variations may be associated with substorm onsets, isolated nightside magnetic impulsive events (MIEs) with ~10 min duration, and Ps6/Pc5 pulsations (periods 3-15 min). For a detailed examination of the latitudinal structure of magnetic variability enhancements and their association with auroral oval boundaries we applied the technique of “magnetic keograms”. This technique helps to visualize the fine structure of a substorm, namely the time and latitudinal localization of dB/dt enhancements. A location of the auroral oval boundaries in a given local time sector has been estimated with the OVATION-prime model based on energetic particle measurements from the DMSP satellites. Auroral substorm onset provided the largest magnetic response on the ground and most intense GIC (few tens of A) when the poleward moving intensification of dB/dt crossed the latitude of power line. Isolated nightside MIEs are also effective in excitation of GICs (>10 A), but they are relatively rare. Quasi-periodic series of MIEs, known as Ps6 / Pi3 pulsations, are effective in excitation of GICs with magnitude about 20 A and even higher. Monochromatic Pc5 pulsations are capable to induce noticeable GICs, up to ~13 A.