scholarly journals UV core dimming in coronal streamer belt and the projection effects

2019 ◽  
Vol 623 ◽  
pp. A95 ◽  
Author(s):  
L. Abbo ◽  
S. Giordano ◽  
L. Ofman
Keyword(s):  
Magnetic Structure ◽  
Heavy Ions ◽  
Solar Minimum ◽  
Heavy Ion ◽  
Spectral Lines ◽  
Slow Solar Wind ◽  
Physical Parameters ◽  
Streamer Belt ◽  
Coronal Streamer ◽  
Tilted Dipole

During solar minimum activity, the coronal structure is dominated by a tilted streamer belt, associated with the sources of the slow solar wind. It is known that some UV coronal spectral observations show a quite evident core dimming in heavy ions emission in quiescent streamers. In this paper, our purpose is to investigate this phenomenon by comparing observed and simulated UV coronal ion spectral line intensities. First, we computed the emissivities and the intensities of HI Lyα and OVI spectral lines starting from the physical parameters of a time-dependent 3D three-fluid MHD model of the coronal streamer belt. The model is applied to a tilted dipole (10°) solar minimum magnetic structure. Next, we compared the results obtained from the model in the extended corona (from 1.5 to 4 R⊙) to the UV spectroscopic data from the Ultraviolet Coronagraph Spectrometer (UVCS) onboard SOHO during the minimum of solar activity (1996). We investigate the line-of-sight integration and projection effects in the UV spectroscopic observations, disentangled by the 3D multifluid model. The results demonstrate that the core dimming in heavy ions is produced by the physical processes included in the model (i.e., combination of the effects of heavy ion gravitational settling, and energy exchange of the preferentially heated heavy ions through the interaction with electrons and protons) but it is visible only in some cases where the magnetic structure is simple, such as a (tilted) dipole.

scholarly journals Three-dimensional multi-fluid model of a coronal streamer belt with a tilted magnetic dipole

2015 ◽  
Vol 33 (1) ◽  
pp. 47-53 ◽  
Author(s):  
L. Ofman ◽  
E. Provornikova ◽  
L. Abbo ◽  
S. Giordano
Keyword(s):  
Solar Wind ◽  
Heavy Ions ◽  
Fluid Model ◽  
Slow Solar Wind ◽  
Streamer Belt ◽  
Lower Corona ◽  
Adequate Model ◽  
Coronal Streamer ◽  
Ion Emission ◽  
D Model

Abstract. Observations of streamers in extreme ultraviolet (EUV) emission with SOHO/UVCS show dramatic differences in line profiles and latitudinal variations in heavy ion emission compared to hydrogen Ly-α emission. In order to use ion emission observations of streamers as the diagnostics of the slow solar wind properties, an adequate model of a streamer including heavy ions is required. We extended a previous 2.5-D multi-species magnetohydrodynamics (MHD) model of a coronal streamer to 3-D spherical geometry, and in the first approach we consider a tilted dipole configuration of the solar magnetic field. The aim of the present study is to test the 3-D results by comparing to previous 2.5-D model result for a 3-D case with moderate departure from azimuthal symmetry. The model includes O5+ ions with preferential empirical heating and allows for calculation of their density, velocity and temperature in coronal streamers. We present the first results of our 3-D multi-fluid model showing the parameters of protons, electrons and heavy ions (O5+) at the steady-state solar corona with a tilted steamer belt. We find that the 3-D results are in qualitative agreement with our previous 2.5-D model, and show longitudinal variation in the variables in accordance with the tilted streamer belt structure. Properties of heavy coronal ions obtained from the 3-D model together with EUV spectroscopic observations of streamers will help understanding the 3-D structures of streamers reducing line-of-sight integration ambiguities and identifying the sources of the slow solar wind in the lower corona. This leads to improved understanding of the physics of the slow solar wind.

scholarly journals Oxygen abundance in coronal streamers during solar minimum

2001 ◽  
Vol 19 (2) ◽  
pp. 135-145 ◽  
Author(s):  
D. Marocchi ◽  
E. Antonucci ◽  
S. Giordano
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Ultra Violet ◽  
Solar Wind Plasma ◽  
Slow Solar Wind ◽  
Streamer Belt ◽  
Oxygen Abundance ◽  
The Core ◽  
Interplanetary Physics ◽  
Slow Wind

Abstract. We present a study of the oxygen abundance relative to hydrogen in the equatorial streamer belt of the solar corona during the recent period of activity minimum. The oxygen abundance is derived from the spectroscopic observations of the outer corona performed during 1996 with the Ultraviolet Coronagraph Spectrometer (SOHO) in the ultra-violet region. This study shows that the depletion of oxygen, by almost one order of magnitude with respect to the photospheric values, found in the inner part of streamers by Raymond et al. (1997a) is a common feature of the solar minimum streamer belt, which exhibits an abundance structure with the following characteristics. In the core of streamers the oxygen abundance is 1.3 × 10-4 at 1.5 R⊙, then it drops to 0.8 × 10-4 at 1.7 R⊙, value which remains almost constant out to 2.2 R⊙. In the lateral bright structures that are ob-served to surround the core of streamers in the oxygen emission, the oxygen abundance drops monotonically with heliodistance, from 3.5 × 10-4 at 1.5 R⊙ to 2.2 × 10-4 at 2.2 R⊙. The oxygen abundance structure found in the streamer belt is consistent with the model of magnetic topology of streamers proposed by Noci et al. (1997). The composition of the plasma contained in streamers is not the same as observed in the slow solar wind. Even in the lateral branches, richer in oxygen, at 2.2 R⊙ the abundance drops by a factor 2 with respect to the slow wind plasma observed with Ulysses during the declining phase of the solar cycle. Hence the slow wind does not appear to originate primarily from streamers, with the exception perhaps of the plasma flowing along the heliospheric current sheet.Key words. Interplanetary physics (solar wind plasma) – Solar physics, astrophysics and astronomy (corona and transition region; ultraviolet emissions)

scholarly journals Diamagnetic and Expansion Effects on the Observable Properties of the Slow Solar Wind in a Coronal Streamer

2005 ◽  
Vol 633 (1) ◽  
pp. 474-488 ◽  
Author(s):  
A. F. Rappazzo ◽  
M. Velli ◽  
G. Einaudi ◽  
R. B. Dahlburg
Keyword(s):  
Solar Wind ◽  
Slow Solar Wind ◽  
Coronal Streamer

scholarly journals INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

2021 ◽  
Vol 26 (4) ◽  
pp. 314-325
Author(s):  
S. V. Stepkin ◽  
◽  
O. O. Konovalenko ◽  
Y. V. Vasylkivskyi ◽  
D. V. Mukha ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Recombination Mechanism ◽  
Radio Recombination Lines ◽  
Radio Spectroscopy ◽  
Correlation Spectrum

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

scholarly journals Diagnostics for spectropolarimetry and magnetography

2010 ◽  
Vol 6 (S273) ◽  
pp. 37-43
Author(s):  
Jose Carlos del Toro Iniesta ◽  
Valentín Martínez Pillet
Keyword(s):  
Analytical Approach ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Instrumental Effects ◽  
Response Functions

AbstractAn assessment on the capabilities of modern spectropolarimeters and magnetographs is in order since most of our astrophysical results rely upon the accuracy of the instrumentation and on the sensitivity of the observables to variations of the sought physical parameters. A contribution to such an assessment will be presented in this talk where emphasis will be made on the use of the so-called response functions to gauge the probing capabilities of spectral lines and on an analytical approach to estimate the uncertainties in the results in terms of instrumental effects. The Imaging Magnetograph eXperiment (IMaX) and the Polarimetric and Helioseismic Imager (PHI) will be used as study cases.

scholarly journals Stopping power of heavy ions in strongly coupled plasmas

1995 ◽  
Vol 13 (2) ◽  
pp. 311-319 ◽  
Author(s):  
G. Zwicknagel ◽  
C. Toepffer ◽  
P.-G. Reinhard
Keyword(s):  
Heavy Ions ◽  
Weak Coupling ◽  
Heavy Ion ◽  
Stopping Power ◽  
Electron Cooling ◽  
Strongly Coupled ◽  
Electron Plasmas ◽  
Coupling Behavior ◽  
Ion Storage ◽  
Coupled Plasmas

We investigate the stopping power of heavy ions in strongly coupled electron plasmas by performing molecular dynamics (MD) computer simulations. A comparison with conventional weak coupling theories shows that these fail in describing the stopping power at low ion velocities and strong coupling. Then nonlinear screening effects become important and this causes a change in the dependence of the stopping power on the ion charge Zp at low ion velocities. From the MD simulation, we find the stopping power to behave like ZP1.43 instead of the weak coupling behavior Zp2 ln(const/Zp). Similar results were recently obtained by experiments in connection with electron cooling at heavy ion storage rings.

scholarly journals Heavy Ion Acceleration at J-PARC

2018 ◽  
Vol 171 ◽  
pp. 21002
Author(s):  
Susumu SATO
Keyword(s):  
High Intensity ◽  
Heavy Ions ◽  
Particle Production ◽  
Heavy Ion ◽  
Proton Accelerator ◽  
Chiral Property ◽  
Region I ◽  
Particle Momentum ◽  
Low Mass ◽  
Frontier Studies

J-PARC, the Japan Proton Accelerator Research Complex, is an accelerator, which provides a high-intensity proton beam. Recently as a very attractive project, the acceleration of heavy ions produced by supplementary ion sources, called J-PARC-HI, is seriously contemplated by domestic as well as international communities. The planned facility would accelerate heavy ions up to U92+ with a beam energy 20 AGeV ([see formula in PDF] of 6.2 AGeV). The highlight of the J-PARC-HI project is its very high beam rate up to ~1011 Hz, which will enable the study of very rare events. Taking advantage of this high intensity, J-PARC-HI will carry out frontier studies of new and rare observables in this energy region: (i) nuclear medium modification of chiral property of vector mesons through low-mass di-lepton signal, (ii) QCD critical pointcharacterization through event-by-event fluctuation signals of particle production, (iii) systematic measurements related to the equation of state through collective flow signal or two-particle momentum correlation signal, or (iv) the search of hyper nuclei with multi strangeness including or exceeding S = 3. The current plan of J-PARC-HI aims to carrying out the first experimental measurements in 2025.

scholarly journals On the influence of CMEs on the global 3-D coronal electron density

2011 ◽  
Vol 29 (6) ◽  
pp. 1019-1028 ◽  
Author(s):  
M. Kramar ◽  
J. Davila ◽  
H. Xie ◽  
S. Antiochos
Keyword(s):  
Electron Density ◽  
Field Configuration ◽  
Line Of Sight ◽  
Streamer Belt ◽  
Coronal Streamer ◽  
First Case ◽  
Before And After ◽  
Coronal Density ◽  
Mass Ejection ◽  
Coronal Electron

Abstract. In order to analize the influence of a Coronal Mass Ejection (CME) on the coronal streamer belt, we made 3-D reconstructions of the electron density in the corona at heliospheric distances from 1.5 to 4 R⊙ for periods before and after a CME occured. The reconstructions were performed using a tomography technique. We studied two CME cases: (i) a slow CME on 1 June 2008; (ii) two fast CMEs on 31 December 2007 and 2 January 2008. For the first case of slow CME, it was found: (i) the potential magnetic field configuration in the CME initiation region before the CME does not agree with the coronal density structure while after the CME the agreement between the field and density is much better. This could be manifistation of that that the field was non-potential before the CME and after the CME the field relaxes towards a more potential state. (ii) It was shown that the dimming caused by the slow CME is not due to rotation of the corona and a line-of-sight (LOS) effect but a streamer blow out effect took place.

Empirical Densities, Kinetic Temperatures, and Outflow Velocities in the Equatorial Streamer Belt at Solar Minimum

2002 ◽  
Vol 571 (2) ◽  
pp. 1008-1014 ◽  
Author(s):  
L. Strachan ◽  
R. Suleiman ◽  
A. V. Panasyuk ◽  
D. A. Biesecker ◽  
J. L. Kohl
Keyword(s):  
Solar Minimum ◽  
Streamer Belt
Sign in / Sign up

Export Citation Format

Share Document