skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: 3D MHD Time-dependent Charge State Ionization and Recombination Modeling of the Bastille Day Coronal Mass Ejection
Heavy ion signatures of coronal mass ejections (CMEs) indicate that rapid and strong heating takes place during the eruption and early stages of propagation. However, the nature of the heating that produces the highly ionized charge states often observed in situ is not fully constrained. An MHD simulation of the Bastille Day CME serves as a test bed to examine the origin and conditions of the formation of heavy ions evolving within the CME in connection with those observed during its passage at L1. In particular, we investigate the bimodal nature of the Fe charge state distribution, which is a quintessential heavy ion signature of CME substructure, as well as the source of the highly ionized plasma. We find that the main heating experienced by the tracked plasma structures linked to the ion signatures examined is due to field-aligned thermal conduction via shocked plasma at the CME front. Moreover, the bimodal Fe distributions can be generated through significant heating and rapid cooling of prominence material. However, although significant heating was achieved, the highest ionization stages of Fe ions observed in situ were not reproduced. In addition, the carbon and oxygen charge state distributions were not well replicated owing to anomalous heavy ion dropouts observed throughout the ejecta. Overall, the results indicate that additional ionization is needed to match observation. An important driver of ionization could come from suprathermal electrons, such as those produced via Fermi acceleration during reconnection, suggesting that the process is critical to the development and extended heating of extreme CME eruptions, like the Bastille Day CME.  more » « less
Award ID(s):
1923365 1923377
PAR ID:
10482144
Author(s) / Creator(s):
; ; ; ; ; ; ;
Publisher / Repository:
American Astronomical Society
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
955
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
65
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal)
    Abstract In this paper we examine a low-energy solar energetic particle (SEP) event observed by IS⊙IS’s Energetic Particle Instrument-Low (EPI-Lo) inside 0.18 au on 2020 September 30. This small SEP event has a very interesting time profile and ion composition. Our results show that the maximum energy and peak in intensity are observed mainly along the open radial magnetic field. The event shows velocity dispersion, and strong particle anisotropies are observed throughout the event, showing that more particles are streaming outward from the Sun. We do not see a shock in the in situ plasma or magnetic field data throughout the event. Heavy ions, such as O and Fe, were detected in addition to protons and 4He, but without significant enhancements in 3He or energetic electrons. Our analysis shows that this event is associated with a slow streamer blowout coronal mass ejection (SBO-CME), and the signatures of this small CME event are consistent with those typical of larger CME events. The time–intensity profile of this event shows that the Parker Solar Probe encountered the western flank of the SBO-CME. The anisotropic and dispersive nature of this event in a shockless local plasma gives indications that these particles are most likely accelerated remotely near the Sun by a weak shock or compression wave ahead of the SBO-CME. This event may represent direct observations of the source of the low-energy SEP seed particle population. 
    more » « less
  2. ; ; ; ; ; ; (, The Astrophysical Journal)
    Abstract In astronomical environments, the high-temperature emission of plasma mainly depends on ion charge states, requiring accurate analysis of the ionization and recombination processes. For various phenomena involving energetic particles, non-Maxwellian distributions of electrons exhibiting high-energy tails can significantly enhance the ionization process. Therefore, accurately computing ionization and recombination rates with non-Maxwellian electron distributions is essential for emission diagnostic analysis. In this work, we report two methods for fitting various non-Maxwellian distributions by using the Maxwellian decomposition strategy. For standardκ-distributions, the calculated ionization and recombination rate coefficients show comparable accuracy to other public packages. Additionally, our methods support arbitrary electron distributions and can be easily extended to updated atomic databases. We apply the above methods to two specific non-Maxwellian distribution scenarios: (i) accelerated electron distributions due to magnetic reconnection revealed in a combined MHD–particle simulation; and (ii) the high-energy truncatedκ-distribution predicted by the exospheric model of the solar wind. During the electron acceleration process, we show that the ionization rates of high-temperature iron ions increase significantly compared to their initial Maxwellian distribution, while the recombination rates may decrease due to the electron distribution changes in low-energy ranges. This can potentially lead to an overestimation of the plasma temperature when analyzing the Fe emission lines under the Maxwellian distribution assumption. For the truncatedκ-distribution in the solar wind, our results show that the ionization rates are lower than those for the standardκ-distribution, while the recombination rates remain similar. This leads to an overestimation of the plasma temperature when assuming aκ-distribution. 
    more » « less
  3. ; (, The Journal of the Utah Academy of Sciences, Arts and Letters)
    Kraus, Kristin L (Ed.)
    A variable specific-impulse magnetoplasma rocket (VASIMR) is a potential means of powering future deep space missions. The engine uses radiofrequency (RF) energy to first ionize argon with a helicon antenna and to subsequently heat the resulting plasma through ion cyclotron heating (ICH) which then creates thrust in a magnetic nozzle. Our previous studies have modeled the increased specific impulse and thrust generated in a collisionless plasma. This work includes ion-neutral collisions in the simulation, which reduces the number of ions in the plasma stream and thus reduces thrust. This study analyzes the loss of thruster efficiency caused by such collisions in the nozzle region of the VASIMR. The plasma is considered weakly ionized, and other plasma effects, such as ion-ion and ion-electron collisions, are ignored. MonteCarlo methods are used to determine ion losses from a stream of individual argon ions as they move along the engine. Neutral densities are inferred from stipulated mass flow rates and ionization fractions. These are functions of the initial ionization process involving a helicon antenna, whose properties are inferred from this study, but not directly dealt with. Ion temperatures, and hence velocities, are determined as products of the ICH process. Efficiency of the engine varies widely with initial mass flow rates and the subsequent neutral backgrounds these produce, but in this simple study, collisional losses are large, for even moderate neutral backgrounds. An effective VASIMR thus requires an extremely efficient initial ionization mechanism. 
    more » « less
  4. ; ; (, The Astrophysical Journal)
    Abstract Anomalous ion heating is frequently observed to accompany magnetic reconnection, yet there is little consensus on its origin. Instead of the usual velocity-space analysis, we use phase-space analysis to exhaustively explain how ions are nonthermally energized during collisionless, antiparallel magnetic reconnection. There are both ordered and disordered aspects in the process; the former is explained in terms of conservative quantities, and the latter is explained by demonstrating chaos through a direct calculation of Lyapunov exponents. The former induces “multibeam-like heating” in all three directions, whereas the latter induces stochastic bulk heating. Profiles of the ion temperature tensor components during reconnection can be easily understood by the phase-space distributions of ions in different motional stages. 
    more » « less
  5. ; ; (, Vacuum)
    A niobium laser multicharged ion source was developed using laser ablation with 10-ns, 1064-nm pulses and a laser fluence of 10–83 Jcm-2. Three distinct groups of Nb ions were detected: ultrafast, fast, and thermal. The ions were accelerated and allowed to drift in a transport line containing an electrostatic ion energy analyzer, a retarding field analyzer, and a Faraday cup. Analysis of the ion energy and charge (z) showed that each group of ions experienced different acceleration potentials during plasma expansion. Time-of-flight (TOF) signal of the thermal ions showed overlap of the signals from Nb1+ and Nb2+. For the fast ion group, z up to Nb7+ was observed and the ion acceleration potential during plasma expansion increased with z, over the charge states from Nb1+ to Nb7+. The TOF signal indicated that the ultrafast ions were composed of higher-charge ions. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email