Events at Physics |
Events on Friday, September 20th, 2024
- Physics Department Colloquium
- Exploring Magnetic Reconnection With Phase Space Measurements
- Time: 3:30 pm - 4:30 pm
- Place: Chamberlin 2241
- Speaker: Earl Scime, West Virginia University
- Abstract: One of the “Grand Challenges” of plasma physics is to understand the processes whereby energy stored in the magnetic fields of a plasma is converted into kinetic energy of the ions and electrons in the plasma. We see that this energy conversion happens in stars, in planetary magnetospheres, and in fusion plasmas. Over the past few decades, there has been considerable progress in developing theoretical models of magnetic reconnection, the process responsible for the energy conversion. Measurements from spacecraft and in laboratory experiments have also contributed to our understanding of magnetic reconnection in collisional and collisionless plasmas. Recently, a variant of magnetic reconnection in which ions do not participate and the physics is dominated by electron dynamics has been identified in space measurements – “electron-only reconnection.” I will review the experimental evidence for electron-only reconnection in space and the state of our computational and theoretical understanding of this process. I will also describe recent studies of electron-only reconnection in the PHAse Space MApping (PHASMA) experiment at West Virginia University. In PHASMA, two magnetic flux ropes are driven together to initiate the reconnection process and advanced, non-perturbative diagnostics provide direct measurements of the electron and ion velocity distribution functions at the kinetic scale (at scales smaller than the gyro motion of the charged particles around the magnetic field). We find that, consistent with theoretical predictions, the majority of incoming magnetic energy appears as electron thermal energy and that Ohmic processes are unlikely to be responsible for the measured increase in electron enthalpy. The electron velocity distribution function measurements include non-Maxwellian features, including beams that jet out from the X-point in both outflow directions. We observe that the electron beam speed scales with the local electron Alfvén speed and that the spatial distribution of the electron heating matches theoretical predictions. Measurements of the three-dimensional electron velocity distribution function (a unique capability of the PHASMA facility) confirm that the most likely mechanism for the electron heating is the parallel electric field created in the reconnection process.
- Host: John Sarff
- WiCOR Speaker Event
- Life in the Cosmic Trenches: The Search for Signs of Life Beyond Earth
- Time: 7:00 pm - 8:00 pm
- Place: 1310 Sterling Hall
- Speaker: Sara Seager, Massachusetts Institute of Technology
- Abstract: For thousands of years, inspired by the star-filled dark night sky, people have wondered what lies beyond Earth. Today, the search for signs of life is a key factor in modern-day planetary exploration. Astronomers have found thousands of planets that orbit nearby stars, called "exoplanets". The newly launched James Webb Space telescope will enable us to study gases in rocky exoplanet atmospheres, including gasses that might be attributed to life.
Followed by star-gazing at Washburn Observatory at 8:30 PM. - Host: WiCOR