scholarly journals Probing Upflowing Regions in the Quiet Sun and Coronal Holes

Solar Physics ◽  
2021 ◽  
Vol 296 (12) ◽  
Author(s):  
Conrad Schwanitz ◽  
Louise Harra ◽  
Nour E. Raouafi ◽  
Alphonse C. Sterling ◽  
Alejandro Moreno Vacas ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Corona ◽  
Extreme Ultraviolet ◽  
Complex Structure ◽  
Coronal Holes ◽  
Variable Structure ◽  
Doppler Velocity ◽  
Small Scale ◽  
Solar Dynamics Observatory ◽  
Complex Behaviour

AbstractRecent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which constantly emit material to feed the wind. In this article we analyse 14 upflow regions in the solar corona to find potential sources for plasma flow. The upflow regions are derived from spectroscopic data from the EUV Imaging Spectrometer (EIS) on board Hinode determining their Doppler velocity and defining regions which have blueshifts stronger than $-6~\mbox{km}\,\mbox{s}^{-1}$ − 6 km s − 1 . To identify the sources of these blueshift data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope (XRT), on board Hinode, are used. The analysis reveals that only 5 out of 14 upflows are associated with frequent transients, like obvious jets or bright points. In contrast to that, seven events are associated with small-scale features, which show a large variety of dynamics. Some resemble small bright points, while others show an eruptive nature, all of which are faint and only live for a few minutes; we cannot rule out that several of these sources may be fainter and, hence, less obvious jets. Since the complex structure of the solar wind is known, this suggests that new sources have to be considered or better methods used to analyse the known sources. This work shows that small and frequent features, which were previously neglected, can cause strong upflows in the solar corona. These results emphasise the importance of the first observations from the Extreme-Ultraviolet Imager (EUI) on board Solar Orbiter, which revealed complex small-scale coronal structures.

scholarly journals Multi-Channel Coronal Hole Detection with Convolutional Neural Networks

2021 ◽  
Author(s):  
Robert Jarolim ◽  
Astrid Veronig ◽  
Stefan Hofmeister ◽  
Stephan Heinemann ◽  
Manuela Temmer ◽  
...  
Keyword(s):  
Neural Network ◽  
Solar Wind ◽  
Coronal Hole ◽  
Source Region ◽  
Coronal Holes ◽  
Small Scale ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics ◽  
Hole Boundary ◽  
The Individual

<p>Being the source region of fast solar wind streams, coronal holes are one of the key components which impact space weather. The precise detection of the coronal hole boundary is an important criterion for forecasting and solar wind modeling, but also challenges our current understanding of the magnetic structure of the Sun. We use deep-learning to provide new methods for the detection of coronal holes, based on the multi-band EUV filtergrams and LOS magnetogram from the AIA and HMI instruments onboard the Solar Dynamics Observatory. The proposed neural network is capable to simultaneously identify full-disk correlations as well as small-scale structures and efficiently combines the multi-channel information into a single detection. From the comparison with an independent manually curated test set, the model provides a more stable extraction of coronal holes than the samples considered for training. Our method operates in real-time and provides reliable coronal hole extractions throughout the solar cycle, without any additional adjustments. We further investigate the importance of the individual channels and show that our neural network can identify coronal holes solely from magnetic field data.</p>

Source-dependent properties of the background slow solar wind encountered by Parker Solar Probe

2021 ◽  
Author(s):  
Léa Griton ◽  
Sarah Watson ◽  
Nicolas Poirier ◽  
Alexis Rouillard ◽  
Karine Issautier ◽  
...  
Keyword(s):  
Solar Wind ◽  
Extreme Ultraviolet ◽  
Plasma Heating ◽  
Coronal Holes ◽  
Slow Solar Wind ◽  
Source Surface ◽  
Field Source ◽  
Flux Tubes ◽  
Field Lines

<p>Different states of the slow solar wind are identified from in-situ measurements by Parker Solar Probe (PSP) inside 50 solar radii from the Sun (Encounters 1, 2, 4, 5 and 6). At such distances the wind measured at PSP has not yet undergone significant transformation related to the expansion and propagation of the wind. We focus in this study on the properties of the quiet solar wind with no magnetic switchbacks. The Slow Solar Wind (SSW) states differ by their density, flux, plasma beta and magnetic pressure. PSP's magnetic connectivity established with Potential Field Source Surface (PFSS) reconstructions, tested against extreme ultraviolet (EUV) and white-light imaging, reveals the different states under study generally correspond to transitions from streamers to equatorial coronal holes. Solar wind simulations run along these differing flux tubes reproduce the slower and denser wind measured in the streamer and the more tenuous wind measured in the coronal hole. Plasma heating is more intense at the base of the streamer field lines rooted near the boundary of the equatorial hole than those rooted closer to the center of the hole. This results in a higher wind flux driven inside the streamer than deeper inside the equatorial hole. </p>

The low-energy ion event on 2020 June 19 measured by Solar Orbiter

2021 ◽  
Author(s):  
Angels Aran ◽  
Daniel Pacheco ◽  
Monica Laurenza ◽  
Nicolas Wijsen ◽  
Evangelia Samara ◽  
...  
Keyword(s):  
Solar Wind ◽  
Energy Range ◽  
Extreme Ultraviolet ◽  
Solar Rotation ◽  
Complex Structure ◽  
Forbush Decrease ◽  
Solar Wind Plasma ◽  
Low Energy ◽  
The European Union ◽  
Horizon 2020

<p>Shortly after reaching the first perihelion, the Energetic Particle Detector (EPD) onboard Solar Orbiter measured a low-energy (<1 MeV/nuc) ion event whose duration varied with the energy of the particles. The increase above pre-event intensity levels was detected early on June 19 for ions in the energy range from ~50 keV to ~1 MeV and lasted up to ~12:00 UT on June 20. In the energy range from ~10 keV to < 40 keV, the ion event spanned from June 18 to 21. This latter low-energy ion intensity enhancement coincided with a two-step Forbush decrease (FD) as displayed in the EPD > 17 MeV/nuc ion measurements. On the other hand, no electron increases were detected. As seen from 1 au, there is no clear evidence of solar activity from the visible disk that could be associated with the origin of this ion event. We hypothesize about the origin of this event as due to either a possible solar eruption occurring behind the visible part of the Sun or to an interplanetary spatial structure. We use interplanetary magnetic field data from the Solar Orbiter Magnetometer (MAG), solar wind electron density derived from measurements of the Solar Orbiter Radio and Plasma Waves (RPW) instrument to specify the in-situ solar wind conditions where the ion event was observed. In addition, we use solar wind plasma measurements from the Solar Orbiter Solar Wind Analyser (SWA) suite gathered during the following solar rotation, for comparison purposes. In order to seek for possible associated solar sources, we use images from the Extreme Ultraviolet Imager (EUI) instrument onboard Solar Orbiter. Together with the lack of electron observations and Type III radio bursts, the simultaneous response of the ion intensity-time profiles at various energies indicates an interplanetary source for the particles. The two-step FD shape observed during this event suggests that the first step early on June 18 was due to a transient structure, whereas the second step on June 19, together with the ~50 –1000 keV/nuc ion enhancement, was due to a solar wind stream interaction region. The observation of a similar FD in the next solar rotation favours this interpretation, although a more complex structure cannot be discarded due to the lack of concurrent solar wind temperature and velocity observations.</p><p>Different parts of this research have received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) and grant agreement No 01004159 (SERPENTINE).</p>

scholarly journals Helioseismology from space, the SOHO project

1988 ◽  
Vol 123 ◽  
pp. 545-548
Author(s):  
V. Domingo
Keyword(s):  
Solar Wind ◽  
Solar Corona ◽  
European Space Agency ◽  
Science Research ◽  
Small Scale ◽  
Heliospheric Observatory ◽  
Space Agency ◽  
Cluster A ◽  
Physics Programme

As a cornerstone of its long term plan for space science research, the European Space Agency (ESA) is developing the Solar Terrestrial Physics Programme that consists of two parts: one, the Solar and Heliospheric Observatory (SOHO) for the study of the solar internal structure and the physics of the solar corona and the solar wind, and another, CLUSTER, a series of four spacecraft flying in formation to study small scale plasma phenomena in several regions of the magnetosphere and in the near Earth solar wind. The feasibility of the missions was demonstrated in Phase A studies carried out by industrial consortia under the supervision of ESA (1,2). According to the current plans an announcement of opportunity calling for instrument proposals will be issued by ESA during the first quarter of 1987. It is foreseen that the spacecraft will be launched by the end of 1994.

scholarly journals The 3D solar corona Cycle 24 rising phase from SDO/AIA tomography

2011 ◽  
Vol 7 (S286) ◽  
pp. 238-241
Author(s):  
Federico A. Nuevo ◽  
Alberto M. Vásquez ◽  
Richard A. Frazin ◽  
Zhenguang Huang ◽  
Ward B. Manchester
Keyword(s):  
Solar Corona ◽  
Extreme Ultraviolet ◽  
Emission Measure ◽  
Source Surface ◽  
Solar Dynamics Observatory ◽  
Differential Emission Measure ◽  
Height Range ◽  
Field Source ◽  
Solar Dynamics ◽  
Cycle 24

AbstractWe recently extended the differential emission measure tomography (DEMT) technique to be applied to the six iron bands of the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory (SDO). DEMT products are the 3D reconstruction of the coronal emissivity in the instrument's bands, and the 3D distribution of the local differential emission measure, in the height range 1.0 to 1.25 R⊙. We show here derived maps of the electron density and temperature of the inner solar corona during the rising phase of solar Cycle 24. We discuss the distribution of our results in the context of open/closed magnetic regions, as derived from a global potential field source surface (PFSS) model of the same period. We also compare the results derived with SDO/AIA to those derived with the Extreme UltraViolet Imager (EUVI) instrument aboard the Solar TErrestrial RElations Observatory (STEREO).

scholarly journals The contribution of X-ray polar blowout jets to the solar wind mass and energy

2013 ◽  
Vol 8 (S300) ◽  
pp. 239-242 ◽  
Author(s):  
Giannina Poletto ◽  
Alphonse C. Sterling ◽  
Stefano Pucci ◽  
Marco Romoli
Keyword(s):  
Solar Wind ◽  
Kinetic Energy ◽  
Energy Budget ◽  
Coronal Mass Ejections ◽  
Mass Flux ◽  
Large Scale ◽  
Coronal Holes ◽  
Magnetic Loop ◽  
Small Scale ◽  
X Ray

AbstractBlowout jets constitute about 50% of the total number of X-ray jets observed in polar coronal holes. In these events, the base magnetic loop is supposed to blow open in what is a scaled-down representation of two-ribbon flares that accompany major coronal mass ejections (CMEs): indeed, miniature CMEs resulting from blowout jets have been observed. This raises the question of the possible contribution of this class of events to the solar wind mass and energy flux. Here we make a first crude evaluation of the mass contributed to the wind and of the energy budget of the jets and related miniature CMEs, under the assumption that small-scale events behave as their large-scale analogs. This hypothesis allows us to adopt the same relationship between jets and miniature-CME parameters that have been shown to hold in the larger-scale events, thus inferring the values of the mass and kinetic energy of the miniature CMEs, currently not available from observations. We conclude our work estimating the mass flux and the energy budget of a blowout jet, and giving a crude evaluation of the role possibly played by these events in supplying the mass and energy that feeds the solar wind.

scholarly journals Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-Era Using CATCH

Solar Physics ◽  
2019 ◽  
Vol 294 (10) ◽  
Author(s):  
Stephan G. Heinemann ◽  
Manuela Temmer ◽  
Niko Heinemann ◽  
Karin Dissauer ◽  
Evangelia Samara ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Coronal Hole ◽  
High Speed ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Central Meridian ◽  
Solar Dynamics Observatory ◽  
Speed Solar Wind ◽  
Solar Dynamics ◽  
Hole Boundary

Abstract Coronal holes are usually defined as dark structures seen in the extreme ultraviolet and X-ray spectrum which are generally associated with open magnetic fields. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints as regards high speed solar wind acceleration processes and compression regions arriving at Earth. In this study we present a new threshold-based extraction method, which incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSW-IDL GUI. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use CATCH to analyze non-polar coronal holes during the SDO-era, based on 193 Å filtergrams taken by the Atmospheric Imaging Assembly (AIA) and magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO). Between 2010 and 2019 we investigate 707 coronal holes that are located close to the central meridian. We find coronal holes distributed across latitudes of about ${\pm}\, 60^{\circ}$±60∘, for which we derive sizes between $1.6 \times 10^{9}$1.6×109 and $1.8 \times 10^{11}\mbox{ km}^{2}$1.8×1011 km2. The absolute value of the mean signed magnetic field strength tends towards an average of $2.9\pm 1.9$2.9±1.9 G. As far as the abundance and size of coronal holes is concerned, we find no distinct trend towards the northern or southern hemisphere. We find that variations in local and global conditions may significantly change the threshold needed for reliable coronal hole extraction and thus, we can highlight the importance of individually assessing and extracting coronal holes.

scholarly journals MHD turbulence and heating of the open field-line solar corona

2003 ◽  
Vol 10 (1/2) ◽  
pp. 93-100 ◽  
Author(s):  
W. H. Matthaeus ◽  
D. J. Mullan ◽  
P. Dmitruk ◽  
L. Milano ◽  
S. Oughton
Keyword(s):  
Solar Corona ◽  
Field Line ◽  
Open Field ◽  
Coronal Holes ◽  
Low Frequency ◽  
Small Scale ◽  
Mhd Turbulence ◽  
Ion Heating ◽  
Open Field Line ◽  
Intense Electron Beams

Abstract. This paper discusses the possibility that heating of the solar corona in open field-line regions emanating from coronal holes is due to a nonlinear cascade, driven by low-frequency or quasi-static magnetohydrodynamic fluctuations. Reflection from coronal inhomogeneities plays an important role in sustaining the cascade. Physical and observational constraints are discussed. Kinetic processes that convert cascaded energy into heat must occur in regions of turbulent small-scale reconnection, and may be similar in some respects to ion heating due to intense electron beams observed in the aurora.

scholarly journals How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation

2003 ◽  
Vol 21 (6) ◽  
pp. 1257-1261 ◽  
Author(s):  
K. Fujiki ◽  
M. Kojima ◽  
M. Tokumaru ◽  
T. Ohmi ◽  
A. Yokobe ◽  
...  
Keyword(s):  
Solar Wind ◽  
Northern Hemisphere ◽  
High Speed ◽  
Solar Maximum ◽  
Complex Structure ◽  
Coronal Holes ◽  
Interplanetary Scintillation ◽  
Wind Structure ◽  
Interplanetary Physics ◽  
Solar Wind Structure

Abstract. Observations from the second Ulysses fast latitude scan show that the global structure of solar wind near solar maximum is much more complex than at solar minimum. Soon after solar maximum, Ulysses observed a polar coronal hole (high speed) plasma with magnetic polarity of the new solar cycle in the Northern Hemisphere. We analyze the solar wind structure at and near solar maximum using interplanetary scintillation (IPS) measurements. To do this, we have developed a new tomographic technique, which improves our ability to examine the complex structure of the solar wind at solar maximum. Our IPS results show that in 1999 and 2000 the total area with speed greater than 700 km s-1 is significantly reduced first in the Northern Hemisphere and then in the Southern Hemisphere. For year 2001, we find that the formation of large areas of fast solar wind around the north pole precedes the formation of large polar coronal holes around the southern pole by several months. The IPS observations show a high level agreement to the Ulysses observation, particularly in coronal holes.Key words. Interplanetary physics (solar wind plasma) – Radio science (remote sensing)

scholarly journals Off-limb EUV observations of the solar corona and transients with the CORONAS-F/SPIRIT telescope-coronagraph

2008 ◽  
Vol 26 (10) ◽  
pp. 3007-3016 ◽  
Author(s):  
V. Slemzin ◽  
O. Bougaenko ◽  
A. Ignatiev ◽  
S. Kuzin ◽  
A. Mitrofanov ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Corona ◽  
White Light ◽  
Extreme Ultraviolet ◽  
Temporal Correlation ◽  
Intermediate Region ◽  
Fast Solar Wind ◽  
Radial Line ◽  
Streamer Belt ◽  
The West

Abstract. The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 Rsun from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 Rsun. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments.

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