PVL Welcomes Three new MSc Students!

This year, three new students are joining PVL at the MSc level through the Physics and Astronomy Graduate Program. Though neither of them worked with the lab in their undergraduate years (and, indeed, come from three different universities) we've already started getting to know them and they us; Grace, Justin and Conor have been able to dial in to our lab meetings over the course of the summer once they moved online due to the pandemic. I know that everyone in the lab is excited to have them join us in an official capacity. They're also keen to introduce themselves to you, dear reader, and wanted to share their experience and hopes for the next couple of years.

Written by Grace Bischof, Conor Hayes and Justin Kerr
Organized by Conor Hayes

Grace Bischof (center in image above) Hi! My name is Grace Bischof and I’m extremely excited to be joining the PVL group as a first year Master’s student this fall. I started my academic career at Western University in London, Ontario and earned my B.S. in physics. I had the privilege of being taught by amazing, passionate physics and astronomy professors who inspired a love for physics (even when it was challenging).  I’m very grateful for the experience I had as an undergraduate student in Physics at Western.

During my undergrad, I participated in research in the area of microfluidics. We designed and tested a T-junction microfluidic device to produce micron-sized beads of human decellularized adipose tissue to be used as a 3-dimensional cell culture method. While I enjoyed the research I participated in, medical physics was not the area of physics that truly interested me.

Like many who do space research, I’ve been captivated with space since I was a kid. When I applied for Master’s programs, I knew that I wanted to do research beyond Earth and was so thrilled to be accepted into this group. In the PVL group, I am going to be involved with the Martian Atmospheric Gas Evolution (MAGE) project. In the lab, we will test an enhanced spectrometer that will (hopefully!) eventually be deployed to Mars to gain a better understanding of the planet’s methane cycle.

I’m looking forward to the next couple of years at York with the PVL group!

Conor Hayes (left in image above) My name is Conor Hayes and I am joining PVL this year as a new Physics and Astronomy M.Sc. student. I received my B.S. in Astronomy and Astrophysics from The Ohio State University in Columbus, Ohio. My research there, through the Center for Cosmology and Astroparticle Physics, was focused primarily on conducting a spectroscopic analysis of five ultra-diffuse galaxy candidates in low-density environments.

My work at PVL will be much closer to home, looking at ices in the permanently shadowed regions (PSRs) of the Moon. PSRs are notable because, as their name implies, they receive very little light from the Sun or other sources, which allows them to protect volatiles like water ice against sublimation on geological timescales. Consequently, PSRs can act as a record of the history of volatiles in the solar system in addition to serving as a potential source of important resources for long-term human inhabitation of other celestial bodies.

When I applied for York’s Physics and Astronomy graduate program, my intent had been to complete the M.Sc. by Coursework degree. However, when I was contacted about the possibility of joining PVL, that plan changed quickly. Although I’ve not yet had substantial experience in planetary science (as it was not an area of much focus in the Department of Astronomy at Ohio State), the study of planets, particularly those closest to home, has held my fascination for quite some time. Consequently, I had to jump on this opportunity when it arose.

Justin Kerr (right in image above) Hi everyone, my name is Justin Kerr and I am a new M.Sc. student with the PVL through York’s Physics and Astronomy program. I am no stranger to York University, as I did my undergrad in Physics and Astronomy here as well. My previous research during that degree primarily consisted of particle physics, with my main project involving searching for magnetic monopoles using the Large Hadron Collider with the ATLAS collaboration. I also hold a BA in History which I completed before returning to university to study physics; my primary areas of interest at the time were Viking Age Scandinavia and medieval Europe. I am now looking forward to bringing my varied experience to the PVL for work in planetary physics.

My work at the PVL will consist of two projects. The first will involve joining the team in the development and testing of the Mars Atmospheric Panoramic camera and Laser Experiment (MAPLE). This project aims to use low-power lasers and a small panoramic camera system to detect small dust and ice particles near the Martian surface. I will also be working on modelling exoplanet atmospheres to determine the size of their “geocorona” (a term normally used to refer to the bubble of hydrogen in the outermost part of Earth’s atmosphere, extending past the orbit of the moon). It is expected that exoplanets possessing water would have an exosphere equivalent to Earth’s geocorona, but we do not yet know whether the size of it is affected by the presence of life. The goal of the project will be to determine what features of these exoplanet “geocoronas” future telescopes should look for as a biosignature when hunting for life-bearing exoplanets. I can’t wait to get started on these two exciting projects with the PVL, and look forward to telling you more about them over my time here.

High-Energy Particle Physics in Thunderstorms

 (the image above depicts a blue jet, a form of upper atmospheric electrical discharge: By Gemini Observatory / AURA - Gemini Observatory / Association of Universities for Research in Astronomy (AURA)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=61319099 )
It's September, a time when new students join our research group. This year we have three and, for the first time, all those students hail from a Physics & Astronomy background. Therefore it is appropriate that one of our new MScs, Justin Kerr, gets first crack at talking about an interesting intersection between high-energy particle physics and planetary science. By way of introduction, I'd love tell you more about the article, but I wouldn't want to steal his thunder! You'll just have to read on...

by Justin Kerr

    Here in Toronto, its currently thunderstorm season. To go along with the high humidity, we’ve had severe storms nearly every week recently reignited my long-held interest. So, when I saw a new paper posted on arXiv last week that covered a new sensor network observing thunderstorms using methods related to my previous research area of particle physics, I simply couldn’t resist digging in to the topic for this week’s post. While it might be surprising to many that high-energy particle physicists would have work to do with thunderstorms, the link between the two fields was experimentally confirmed in the 1980s. Even so, most of the knowledge about exactly how thunderstorms produce high energy particles is still hypothetical due to the difficulty of observing large thunderstorms. This is something the new paper sought to address.
    But first, let’s take a look what high-energy particles are produced by thunderstorms and how that might be happening. The first type of high-energy event being produced by thunderstorms is the terrestrial gamma-ray flash (TGF), which are rapid bursts lasting less than a millisecond. TGFs are expected to occur when an already energetic electron (likely produced by a cosmic ray entering the thunderstorm) is accelerated to near the speed of light by the intense electric field created by a lightning strike. This relativistic electron then begins a process known as a relativistic runaway electron avalanche (RREA). The RREA process consists of the initial electron colliding with the electrons surrounding atoms in the atmosphere with enough energy to knock them off. These electrons are then accelerated themselves and go on to knock off even more electrons in a chain reaction, creating a massive “avalanche” of high-energy electrons. As the electrons produced by RREA are slowed down by collisions with atomic nuclei in the atmosphere, they produce gamma rays via the Bremsstrahlung process. The gamma rays then escape upwards, where they can be detected by aircraft or satellites. 

Figure 1: Expected method of TGF formation at the top of a thundercloud. Source: https://en.wikipedia.org/wiki/Terrestrial_gamma-ray_flash#/media/File:TGF_production_by_quasi-static_fields.svg

    Several satellites have now recorded measurements of TGFs. They were first discovered by the Compton Gamma-Ray Observatory in 1994. In the 2000s, the RHESSI experiment showed the electrons could reach energies exceeding 20 MeV – which is in the range of the highest energies produced in linear accelerators for medical radiotherapy. Even more recently, the Fermi Gamma-ray Space Telescope discovered evidence of antimatter production from TGFs in 2009. When a positron meets an electron, the two annihilate and produce two photons each with an energy of 0.511 MeV (the energy equivalent of the rest mass of an electron/positron). The positrons have been experimentally shown to be produced when photons of energies exceeding 10 MeV trigger photonuclear reactions in atmospheric nuclei, creating radioactive nuclei and free neutrons. When positrons created in the TGF process either traveled directly upwards or rode along Earth’s magnetic field to the spacecraft they annihilated with electrons in the spacecraft, allowing it to see the telltale 0.511 MeV photons in its gamma ray detector. The Fermi team was able to trace these incoming positrons back along Earth’s magnetic field lines to specific thunderstorms producing them. With Fermi’s detection of numerous TGFs, it is now estimated that about 500 TGFs occur every day worldwide. Recently some rare TGFs have even been detected going downwards towards the ground, potentially opening up new opportunities to better study their formation.
    The second type of high-energy event known to be occurring in thunderstorms is gamma-ray glow. Gamma-ray glow was discovered by x-ray observations from aircraft above thunderstorms in the 1980s. This glow is much longer lasting than a TGF, with events potentially lasting tens of minutes. Energetic particles in a glow can reach similar energies to that of TGFs and are expected to be produced by the same RREA process. Unfortunately, the production of gamma-ray glow is somewhat less understood than that of TGFs. The glow seems to be produced by long-lasting stable electric fields in thunderclouds, and it is usually terminated when a lightning strike dissipates the stable field.
    The good news is that the ground-directed nature of gamma-ray glow is now providing new opportunities to study high-energy processes in thunderstorms without the need for difficult and expensive observations from above. While gamma ray photons are normally absorbed by the atmosphere in about 1km and thus long before they reach the ground from a typical thunderstorm, the Thundercloud Project in Japan has a way around this. In the winter, Japan has thunderstorms with cloud bases at heights of less than 1km and so ground based observations of their high-energy particles can be made. By assembling a network of sensors around Ishikawa Prefecture and Niigata Prefecture in Japan, they were able to record 51 gamma-ray events in the last four years. From this data, they have been able to show distinctive evidence of gamma-glow termination by lightning strikes. They were also able to detect a few downward TGFs, which show time-resolved proof of photonuclear reactions producing free neutrons and positrons. Their full results are currently in pre-print and set to be published in Progress of Theoretical and Experimental Physics.
    With the new results from the Thundercloud Project and hopefully more studies to come, we will be able to significantly advance our understanding of the processes involved in the high-energy phenomena of thunderstorms. It is certainly amazing how much there still is to learn about thunderstorms occurring right here on Earth, and how something so standard in our daily lives can be utilizing processes which we previously thought were restricted to particle accelerators or high-energy astrophysical phenomena. So the next time you hear an approaching thunderstorm, remember that you don’t need to travel to CERN or Fermilab to witness high-energy physics in action!

Sources: https://www.nasa.gov/mission_pages/GLAST/news/fermi-thunderstorms.html,
https://arxiv.org/pdf/2007.13618.pdf,
https://www.nature.com/articles/s42005-019-0168-y,
https://en.wikipedia.org/wiki/Terrestrial_gamma-ray_flash