September 15, 2017, 1:00 pm - 2:00 pm

September 15, 2017, 1:00 pm - 2:00 pm, Heliophysics Director's Seminar, Hosted by the Heliospheric Physics Laboratory (672)

The Solar Wind's Ion Suprathermal Tail

Brent Randol

The velocity distribution function (VDF) of solar wind protons (as well as other ion populations) is comprised of a thermal Maxwellian core and an accelerated suprathermal tail, beginning at around 1 keV in the frame co-moving with solar wind bulk velocity. The form of the suprathermal tail is a power law in phase space density, f, vs. speed, v, such that f ~ v-5. This commonly observed index is of particular interest because no traditional theory predicts its existence. We show observations from the STICS instrument on the WIND spacecraft. After fitting a general power law with an exponential roll-over at high energies to these data, we find rough consistency with previously reported studies. We also discuss potential explanations for this observation.

Investigating the Dynamics and Loss of Energetic Electrons in Earth's Radiation Belts through Multipoint Measurements

Lauren Blum

The Van Allen radiation belts, composed of energetic ions and electrons trapped around the Earth, often exhibit dramatic variations in intensity and spatial extent. Characterization of the processes contributing to electron acceleration and loss in this region is critical to understanding the variable near-Earth space environment. Here, we investigate the contribution of electron precipitation into the atmosphere to radiation belt dynamics and losses. Utilizing the growing constellation of spacecraft in Earth's magnetosphere, including recent CubeSat and balloon measurements, we explore the nature and extent of electron loss to the atmosphere as well as what electromagnetic wave modes may be causing it. These studies aid in the understanding of outer radiation belt dynamics and the relationship between precipitating energetic electrons, electromagnetic waves, and global magnetospheric conditions.

The Interesting Immediate Effects of Interplanetary Shocks on Energetic Particles in Earth's Magnetosphere

Quintin Schiller

Interplanetary shocks that impact Earth's magnetosphere can have impressive effects on energetic particles in Earth's inner magnetosphere. Within a few minutes of impact, the shock can cause a dramatic Earthward injection of electrons, which is a significant source of relativistic and highly relativistic electrons in Earth's magnetosphere. This process is also the most powerful magnetospheric acceleration mechanism, capable of accelerating electrons to 50MeV and injecting them inwards of L=2.6. However, not all shock impacts cause enhancements, and some can even cause electron depletions instead. The relationships between shock parameters and particle enhancements are just beginning to be unraveled.