Annual Meeting of the APS Division of Plasma Physics

The 63rd Annual Meeting of the APS Division of Plasma Physics was held from Monday to Friday, November 8–12, 2021 in Pittsburgh, PA. During the meeting two sessions of the Mini-Conference on Collisionless Shocks in Laboratory and Space Plasmas were organized (co-conveners: N. Pogorelov, M. Gedalin (SHARP), D. Schaeffer). Most of the topics of the mini-confererence were directly relevant to the research within SHARP.

The talk CM10.00007: Modeling Solar Wind Interaction with the Local Interstellar Medium using Kinetically-Derived Rankine-Hugoniot Conditions for Pickup Ions (N. Pogorelov, M. Gedalin (SHARP), V. S. Roytershteyn, R. K. Bera, F. Fraternale, W. P. Smith, M. Zhang) includes the results obtained by M. Gedalin within the work on Workpackage 2 and 3.
The talk CM10.00006: Kinetic Simulations of the Behavior of Pickup Ions in the Vicinity of a Collisionless Shock (V. S. Roytershteyn, P. F. Kilian, M. Gedalin (SHARP), N. Pogorelov) is also related to the research within the SHARP project.

SHARP involved in new publication on ultralow frequency wave transmission across collisionless shocks

We address the problem of what happens to upstream ultralow frequency (ULF) waves as they reach shocks and are carried into the downstream region. We do this by analyzing the results of 11 2.5D local hybrid simulations of collisionless shocks. We find that the waves are not simply transmitted into the downstream region but that their identity is largely destroyed, as the downstream fluctuations do not resemble the upstream waves neither in wavelengths nor in appearance. However, some features observed in the Fourier spectra of upstream ULF waves are conserved in the Fourier spectra of compressive downstream fluctuations.

Full article:
Kajdič, P., Pfau-Kempf, Y., Turc, L., Dimmock, A. P., Palmroth, M., Takahashi, K., et al. (2021). ULF wave transmission across collisionless shocks: 2.5D local hybrid simulations. Journal of Geophysical Research: Space Physics, 126, doi: 10.1029/2021JA029283

Dmitry Prokhorov and Emanuele Greco joined the SHARP team this autumn

In September, Dmitry Prokhorov started to work on X-ray polarimetry in the group led by Jacco Vink at the University of Amsterdam (UvA). Dmitry will analyze data from the Imaging X-ray Polarimetry Explorer for performing a polarimetric study of supernova remnants to characterize particle acceleration at their shock fronts.

As of October, Emanuele Greco joined UvA as a member of the SHARP team. He will deal with non-thermal emission due to synchrotron radiation in supernova remnants by analyzing observations collected in the X-ray energy band. In particular, he will look for spectral signatures of jittering radiation in young remnants such as Cassiopeia A, Tycho and SN 1006.

New Publication: “Shock Mach Number Estimates Using Incomplete Measurements” by Michael Gedalin et al.

The Mach number is one of the most important parameters of collisionless shocks. The accuracy of its observational determination is compromised by several complications. Incomplete measurements of plasma parameters significantly contribute to the uncertainty, along with the errors of the normal determination. A set of CLUSTER observed shocks is analyzed using several methods for finding the shock normal and to circumvent the shortcomings of the plasma data. A relation between the maximum magnetic compression and the Alfvénic Mach number is established. It is proposed as a proxy for the Mach number estimate when measurements are incomplete.

Theoretical proxy for the Mach number.

Full article:
Gedalin, M., Russell, C. T., Dimmock, A. P. (2021). Shock Mach number estimates using incomplete measurements. Journal of Geophysical Research: Space Physics, 126, doi: 10.1029/2021JA029519

License: CC BY-NC-ND 4.0

SHARP at GEM 2021 Summer workshop

Andrew Dimmock gave a presentation entitled “An MMS bow shock database using machine learning: EU H2020 SHARP project” at the summer GEM virtual workshop ( in the focus group “Particle Heating and Thermalization in Collisionless Shocks in the MMS Era”. The presentation provided details of the identification of terrestrial bow shocks using machine learning classification of the ion phase space distribution functions and the SHARP project. An overview of the SHARP terrestrial database was presented, as well as quick look plots, and the online functionality available to the wider community.

Click here to view the presentation or visit the Publications and Presentations page.

New Publication: “The Post-impact Evolution of the X-Ray-emitting Gas in SNR 1987A as Viewed by XMM-Newton” by Lei Sun et al.

Since 1996 the blast wave driven by SN 1987A has been interacting with the dense circumstellar material, which provides us with a unique opportunity to study the early evolution of a newborn supernova remnant (SNR). Based on the XMM-Newton RGS and EPIC-pn X-ray observations from 2007 to 2019, we investigated the post-impact evolution of the X-ray-emitting gas in SNR 1987A. The hot plasma is represented by two nonequilibrium ionization components with temperatures of ~0.6 keV and ~2.5 keV. The low-temperature plasma has a density ~2400 cm−3, which is likely dominated by the lower-density gas inside the equatorial ring (ER). The high-temperature plasma with a density ~550 cm−3 could be dominated by the H ii region and the high-latitude material beyond the ring. In the last few years, the emission measure of the low-temperature plasma has been decreasing, indicating that the blast wave has left the main ER. But the blast wave is still propagating into the high-latitude gas, resulting in the steady increase of the high-temperature emission measure. Meanwhile, the average abundances of N, O, Ne, and Mg are found to be declining, which may reflect the different chemical compositions between the two plasma components. We also detected Fe K lines in most of the observations, showing increasing flux and centroid energy. We interpret the Fe K lines as originating from a third hot component, which may come from the reflected shock heated gas or originate from Fe-rich ejecta clumps shocked by the reverse shock.

EPIC-pn images of SNR 1987A region. The source and background extraction regions used for the spectral analysis are denoted by red and white circles, respectively.

Full article:
Lei Sun et al (2021), The Post-impact Evolution of the X-Ray-emitting Gas in SNR 1987A as Viewed by XMM-Newton, The Astrophysical Journal, 916(1), doi: 10.3847/1538-4357/ac033d

License: CC BY 4.0

New publication: “Spatially Resolved RGS Analysis of Kepler’s Supernova Remnant” by Tomoaki Kasuga et al.

The distribution and kinematics of the circumstellar medium (CSM) around a supernova remnant (SNR) tell us useful information about the explosion of its natal supernova (SN). Kepler’s SNR, the remnant of SN 1604, is widely regarded to be of Type Ia origin. Its shock is moving through a dense, asymmetric CSM. The presence of this dense gas suggests that its parent progenitor system consisted of a white dwarf and an asymptotic giant branch (AGB) star. In this paper, we analyze a new and long observation with the reflection grating spectrometers on board the XMM-Newton satellite, spatially resolving the remnant emission in the cross-dispersion direction. We find that the CSM component is blueshifted with velocities in the general range 0–500 km s−1. We also derive information on the central bar structure and find that the northwest half is blueshifted, while the southeast half is redshifted. Our result is consistent with a picture proposed by previous studies, in which a “runaway” AGB star moved to the north-northwest and toward us in the line of sight, although it is acceptable for both single- and core-degenerate scenarios for the progenitor system.

Full article:
Tomoaki Kasuga et al (2021), Spatially Resolved RGS Analysis of Kepler’s Supernova Remnant, The Astrophysical Journal, 915(1), doi: 10.3847/1538-4357/abff4f