Doppler shifts of solar UV emission lines and the source region of the (fast) solar wind

1999 ◽  
Author(s):  
Hardi Peter
Keyword(s):  
Solar Wind ◽  
Source Region ◽  
Emission Lines ◽  
Fast Solar Wind ◽  
Doppler Shifts ◽  
Uv Emission ◽  
Solar Uv

scholarly journals New deep coronal spectra from the 2017 total solar eclipse

2019 ◽  
Vol 632 ◽  
pp. A86 ◽  
Author(s):  
S. Koutchmy ◽  
F. Baudin ◽  
Sh. Abdi ◽  
L. Golub ◽  
F. Sèvre
Keyword(s):  
Solar Wind ◽  
Solar Eclipse ◽  
Coronal Holes ◽  
Solar Limb ◽  
Total Solar Eclipse ◽  
Emission Lines ◽  
High Spectral Resolution ◽  
Doppler Shifts ◽  
Dust Component ◽  
The Continuum

Context. The origin of the high temperature of the solar corona, in both the inner bright parts and the more outer parts showing flows toward the solar wind, is not understood well yet. Total eclipses permit a deep analysis of both the inner and the outer parts of the corona using the continuum white-light (W-L) radiations from electrons (K-corona), the superposed spectrum of forbidden emission lines from ions (E-corona), and the dust component with F-lines (F-corona). Aims. By sufficiently dispersing the W-L spectrum, the Fraunhofer (F) spectrum of the dust component of the corona appears and the continuum Thomson radiation can be evaluated. The superposed emission lines of ions with different degrees of ionization are studied to allow the measurement of temperatures, non-thermal velocities, Doppler shifts, and abundances to constrain the proposed heating mechanisms and understand the origin of flows that lead to solar wind. Methods. We describe a slit spectroscopic experiment of high spectral resolution to provide an analysis of the most typical parts of the quasi-minimum type corona observed during the total solar eclipse of Aug. 21, 2017 from Idaho, USA. Streamers, active region enhancements, and polar coronal holes (CHs) are measured well using deep spectra. Results. Sixty spectra are obtained during the totality with a long slit, covering ±3 solar radii in the range of 510 nm to 590 nm. The K+F continuum corona is exposed well up to two solar radii. The F-corona can be measured even at the solar limb. New weak emission lines were discovered or confirmed. The rarely observed Ar X line is detected almost everywhere; the Fe XIV and Ni XIII lines are clearly detected everywhere. For the first time hot lines are also measured inside the CH regions. The radial variations of the non-thermal turbulent velocities of the lines do not show a great departure from the average values. No significantly large Doppler shifts are seen anywhere in the inner or the middle corona. The wings of the Fe XIV line show some non-Gaussianity. Conclusions. Deep slit coronal spectra offered an opportunity for diagnosing several aspects of coronal physics during a well observed total eclipse without extended investments. The analysis of the ionic emission line profiles offers several powerful diagnostics of the coronal dynamics; the precise measurement of the F-continuum component provides insight into the ubiquitous dust corona at the solar limb.

scholarly journals Cluster observations of near-Earth magnetospheric lobe plasma densities – a statistical study

2008 ◽  
Vol 26 (9) ◽  
pp. 2845-2852 ◽  
Author(s):  
K. R. Svenes ◽  
B. Lybekk ◽  
A. Pedersen ◽  
S. Haaland
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Source Region ◽  
Wind Condition ◽  
Quiet Time ◽  
Polar Wind ◽  
Spacecraft Potential ◽  
Solar Uv ◽  
Two Parameters

Abstract. The Cluster-mission has enabled a study of the near-Earth magnetospheric lobes throughout the waning part of solar cycle 23. During the first seven years of the mission the satellites crossed this region of space regularly from about July to October. We have obtained new and more accurate plasma densities in this region based on spacecraft potential measurements from the EFW-instrument. The plasma density measurements are found by converting the potential measurements using a functional relationship between these two parameters. Our observations have shown that throughout this period a full two thirds of the measurements were contained in the range 0.007–0.092 cm−3 irrespective of solar wind conditions or geomagnetic activity. In fact, the most probable density encountered was 0.047 cm−3, staying roughly constant throughout the entire observation period. The plasma population in this region seems to reflect an equilibrium situation in which the density is independent of the solar wind condition or geomagnetic activity. However, the high density tail of the population (ne>0.2 cm−3) seemed to decrease with the waning solar cycle. This points to a source region influenced by the diminishing solar UV/EUV-intensity. Noting that the quiet time polar wind has just such a development and that it is magnetically coupled to the lobes, it seems likely to assume that this is a prominent source for the lobe plasma.

Observations of the profiles of solar UV emission lines and their analysis in terms of the heating and production of the corona

1972 ◽  
Vol 13 (4-6) ◽  
pp. 639-641 ◽  
Author(s):  
B. C. Boland ◽  
S. F. T. Engstrom ◽  
B. B. Jones ◽  
R. W. P. McWhirter ◽  
P. C. Thonemann ◽  
...  
Keyword(s):  
Emission Lines ◽  
Uv Emission ◽  
Solar Uv

Modeling proton and electron heating in the fast solar wind

2020 ◽  
Author(s):  
L. Adhikari ◽  
G.P. Zank ◽  
L.-L. Zhao ◽  
M. Nakanotani ◽  
S. Tasnim
Keyword(s):  
Solar Wind ◽  
Fast Solar Wind ◽  
Electron Heating

Correlation Height of the Source Region of Si II Emission Lines in Coronal Hole Regions

2007 ◽  
Vol 31 (2) ◽  
pp. 137-145
Author(s):  
Gui-qing Zhou ◽  
Jian-sen He ◽  
Chuan-yi Tu ◽  
E. Marsch
Keyword(s):  
Coronal Hole ◽  
Source Region ◽  
Emission Lines

Proton Beam Abundance Variations and Their Relation to Alpha Particle Properties

2021 ◽  
Vol 923 (2) ◽  
pp. 170
Author(s):  
Tereza Ďurovcová ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Proton Beam ◽  
Alpha Particle ◽  
Source Region ◽  
Radial Distance ◽  
Alpha Particles ◽  
Momentum Balance ◽  
Particle Interactions ◽  
Coulomb Collisions ◽  
Particle Properties

Abstract Less abundant but still dynamically important solar wind components are the proton beam and alpha particles, which usually contribute similarly to the total ion momentum. The main characteristics of alpha particles are determined by the solar wind source region, but the origin of the proton beam and its properties are still not fully explained. We use the plasma data measured in situ on the path from 0.3 to 1 au (Helios 1 and 2) and focus on the proton beam development with an increasing radial distance as well as on the connection between the proton beam and alpha particle properties. We found that the proton beam relative abundance increases with increasing distance from the Sun in the collisionally young streams. Among the mechanisms suggested for beam creation, we have identified the wave–particle interactions with obliquely propagating Alfvén modes being consistent with observations. As the solar wind streams get collisionally older, the proton beam decay gradually dominates and the beam abundance is reduced. In search for responsible mechanisms, we found that the content of alpha particles is correlated with the proton beam abundance, and this effect is more pronounced in the fast solar wind streams during the solar maximum. We suggest that Coulomb collisions are the main agent leading to merging of the proton beam and core. We are also showing that the variations of the proton beam abundance are correlated with a decrease of the alpha particle velocity in order to maintain the total momentum balance in the solar wind frame.

scholarly journals ELEMENTAL ABUNDANCES IN THE FAST SOLAR WIND EMANATING FROM CHROMOSPHERIC FUNNELS

2010 ◽  
Vol 709 (2) ◽  
pp. 993-1002 ◽  
Author(s):  
Stefano Pucci ◽  
Øystein Lie-Svendsen ◽  
Ruth Esser
Keyword(s):  
Solar Wind ◽  
Fast Solar Wind ◽  
Elemental Abundances

scholarly journals Uncertainties of the solar wind in-situ velocity measurements

2020 ◽  
pp. 193-197
Author(s):  
G. Gogoberidze ◽  
E. Gorgaslidze
Keyword(s):  
Solar Wind ◽  
Independent Method ◽  
Inertial Range ◽  
Velocity Measurements ◽  
Fast Solar Wind ◽  
Magnetohydrodynamic Turbulence ◽  
Velocity Fluctuations ◽  
Measurement Uncertainties ◽  
General Instrument

We study spectral features of Alfvénic turbulence in fast solar wind. We propose a general, instrument independent method to estimate the uncertainty in velocity fluctuations obtained by in-situ satellite observations in the solar wind. We show that when the measurement uncertainties of the velocity fluctuations are taken into account the less energetic Elsasser spectrum obeys a unique power law scaling throughout the inertial range as prevailing theories of magnetohydrodynamic turbulence predict.

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