The impact of coronal hole characteristics and solar cycle activity in reconstructing coronal holes with EUHFORIA

AbstractWe study the properties of coronal holes during solar cycle 21-23 from the McIntosh archive. In the spatial distribution of coronal hole area we find that there is a sharp increase in coronal hole area at high latitude in agreement with expected open flux configuration there. In overall spatiotemporal distribution of coronal hole centroids, we find the dominance of high latitude coronal holes except for the maximum of the solar cycle, when coronal holes mostly appear in low latitudes. This is in agreement with the expected solar cycle evolution of surface magnetic flux.

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Statistical Approach on Differential Emission Measure of Coronal Holes using the CATCH Catalog

Solar Physics ◽

10.1007/s11207-020-01759-0 ◽

2021 ◽

Vol 296 (1) ◽

Author(s):

Stephan G. Heinemann ◽

Jonas Saqri ◽

Astrid M. Veronig ◽

Stefan J. Hofmeister ◽

Manuela Temmer

Keyword(s):

Solar Cycle ◽

Coronal Hole ◽

Electron Density ◽

Large Scale ◽

Scattered Light ◽

Coronal Holes ◽

Emission Measure ◽

Solar Dynamics Observatory ◽

Differential Emission Measure ◽

Plasma Properties

AbstractCoronal holes are large-scale structures in the solar atmosphere that feature a reduced temperature and density in comparison to the surrounding quiet Sun and are usually associated with open magnetic fields. We perform a differential emission measure analysis on the 707 non-polar coronal holes in the Collection of Analysis Tools for Coronal Holes (CATCH) catalog to derive and statistically analyze their plasma properties (i.e. temperature, electron density, and emission measure). We use intensity filtergrams of the six coronal EUV filters from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, which cover a temperature range from $\approx10^{5.5}$ ≈ 10 5.5 to $10^{7.5}~\mbox{K}$ 10 7.5 K . Correcting the data for stray and scattered light, we find that all coronal holes have very similar plasma properties with an average temperature of $0.94 \pm0.18~\mbox{MK}$ 0.94 ± 0.18 MK , a mean electron density of $(2.4 \pm0.7) \times10^{8}~\mbox{cm}^{-3}$ ( 2.4 ± 0.7 ) × 10 8 cm − 3 , and a mean emission measure of $(2.8 \pm1.6) \times10^{26}~\mbox{cm}^{-5}$ ( 2.8 ± 1.6 ) × 10 26 cm − 5 . The temperature distribution within the coronal holes was found to be largely uniform, whereas the electron density shows a 30 to 40% linear decrease from the boundary towards the inside of the coronal hole. At distances greater than 20″ ($\approx15~\mbox{Mm}$ ≈ 15 Mm ) from the nearest coronal hole boundary, the density also becomes statistically uniform. The coronal hole temperature may show a weak solar-cycle dependency, but no statistically significant correlation of plasma properties with solar-cycle variations could be determined throughout the observed period between 2010 and 2019.

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On the Location of Quiescent Prominences with Respect to Coronal Holes

International Astronomical Union Colloquium ◽

10.1017/s0252921100065507 ◽

1979 ◽

Vol 44 ◽

pp. 209-213

Author(s):

B. Rompolt

Keyword(s):

Coronal Hole ◽

Average Distance ◽

Coronal Holes

The aim of this contribution is to turn attention to a peculiarity of location of the filaments (quiescent prominences) with respect to the boundaries of the coronal holes. It is generally known that quiescent prominences are located at some distance from the boundary of coronal holes. My intention was to check whether the average distance between the nearest border of a coronal hole and the prominence is comparable to the average horizontal extension of a helmet structure overlying the prominence. As well as, whether this average distance depends upon the orientation of the long axis of the prominence with respect to the nearest boundary of the coronal hole.

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The Evolution of the Solar Magnetic Field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314004670 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 86-89 ◽

Cited By ~ 2

Author(s):

J. Todd Hoeksema

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Solar Magnetic Field ◽

Coronal Holes ◽

Active Regions ◽

Statistical Characteristics ◽

Field Pattern ◽

Small Scale ◽

Polar Caps ◽

Magnetic Elements

AbstractThe almost stately evolution of the global heliospheric magnetic field pattern during most of the solar cycle belies the intense dynamic interplay of photospheric and coronal flux concentrations on scales both large and small. The statistical characteristics of emerging bipoles and active regions lead to development of systematic magnetic patterns. Diffusion and flows impel features to interact constructively and destructively, and on longer time scales they may help drive the creation of new flux. Peculiar properties of the components in each solar cycle determine the specific details and provide additional clues about their sources. The interactions of complex developing features with the existing global magnetic environment drive impulsive events on all scales. Predominantly new-polarity surges originating in active regions at low latitudes can reach the poles in a year or two. Coronal holes and polar caps composed of short-lived, small-scale magnetic elements can persist for months and years. Advanced models coupled with comprehensive measurements of the visible solar surface, as well as the interior, corona, and heliosphere promise to revolutionize our understanding of the hierarchy we call the solar magnetic field.

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Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5045-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 5045-5077 ◽

Cited By ~ 60

Author(s):

K. Semeniuk ◽

V. I. Fomichev ◽

J. C. McConnell ◽

C. Fu ◽

S. M. L. Melo ◽

...

Keyword(s):

Solar Cycle ◽

Radiative Forcing ◽

Climate Model ◽

Middle Atmosphere ◽

High Energy ◽

Galactic Cosmic Rays ◽

Particle Precipitation ◽

Solar Cycle Variation ◽

Cycle Variation ◽

The Impact

Abstract. The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), auroral zone medium and high energy electrons, solar proton events and galactic cosmic rays on the middle atmosphere is examined using a chemistry climate model. This process study uses ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10 % in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4 % more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

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The representation of solar cycle signals in stratospheric ozone. Part II: Analysis of global models

10.5194/acp-2017-477 ◽

2017 ◽

Cited By ~ 3

Author(s):

Amanda C. Maycock ◽

Katja Matthes ◽

Susann Tegtmeier ◽

Hauke Schmidt ◽

Rémi Thiéblemont ◽

...

Keyword(s):

Solar Cycle ◽

Solar Irradiance ◽

Climate Models ◽

Climate Model ◽

Stratospheric Ozone ◽

Temperature Response ◽

Solar Variability ◽

High Latitudes ◽

Stratospheric Temperature ◽

The Impact

Abstract. The impact of changes in incoming solar irradiance on stratospheric ozone abundances should be included in climate model simulations to fully capture the atmospheric response to solar variability. This study presents the first systematic comparison of the solar-ozone response (SOR) during the 11 year solar cycle amongst different chemistry-climate models (CCMs) and ozone databases specified in climate models that do not include chemistry. We analyse the SOR in eight CCMs from the WCRP/SPARC Chemistry-Climate Model Initiative (CCMI-1) and compare these with three ozone databases: the Bodeker Scientific database, the SPARC/AC&C database for CMIP5, and the SPARC/CCMI database for CMIP6. The results reveal substantial differences in the representation of the SOR between the CMIP5 and CMIP6 ozone databases. The peak amplitude of theSOR in the upper stratosphere (1–5 hPa) decreases from 5 % to 2 % between the CMIP5 and CMIP6 databases. This difference is because the CMIP5 database was constructed from a regression model fit to satellite observations, whereas the CMIP6 database is constructed from CCM simulations, which use a spectral solar irradiance (SSI) dataset with relatively weak UV forcing. The SOR in the CMIP6 ozone database is therefore implicitly more similar to the SOR in the CCMI-1 models than to the CMIP5 ozone database, which shows a greater resemblance in amplitude and structure to the SOR in the Bodeker database. The latitudinal structure of the annual mean SOR in the CMIP6 ozone database and CCMI-1 models is considerably smoother than in the CMIP5 database, which shows strong gradients in the SOR across the midlatitudes owing to the paucity of observations at high latitudes. The SORs in the CMIP6 ozone database and in the CCMI-1 models show a strong seasonal dependence, including large meridional gradients at mid to high latitudes during winter; such seasonal variations in the SOR are not included in the CMIP5 ozone database. Sensitivity experiments with a global atmospheric model without chemistry (ECHAM6.3) are performed to assess the impact of changes in the representation of the SOR and SSI forcing between CMIP5 and CMIP6. The experiments show that the smaller amplitude of the SOR in the CMIP6 ozone database compared to CMIP5 causes a decrease in the modelled tropical stratospheric temperature response over the solar cycle of up to 0.6 K, or around 50 % of the total amplitude. The changes in the SOR explain most of the difference in the amplitude of the tropical stratospheric temperature response in the case with combined changes in SOR and SSI between CMIP5 and CMIP6. The results emphasise the importance of adequately representing the SOR in climate models to capture the impact of solar variability on the atmosphere. Since a number of limitations in the representation of the SOR in the CMIP5 ozone database have been identified, CMIP6 models without chemistry are encouraged to use the CMIP6 ozone database to capture the climate impacts of solar variability.

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Impact of nonlinear surface inflows into activity belts on the solar dynamo

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2020064 ◽

2020 ◽

Vol 10 ◽

pp. 62

Author(s):

Melinda Nagy ◽

Alexandre Lemerle ◽

Paul Charbonneau

Keyword(s):

Solar Cycle ◽

Magnetic Flux ◽

Activity Cycle ◽

Surface Flux ◽

Meridional Flow ◽

Cycle Model ◽

Flux Transport ◽

Bona Fide ◽

Nonlinear Surface ◽

The Impact

We examine the impact of surface inflows into activity belts on the operation of solar cycle models based on the Babcock–Leighton mechanism of poloidal field regeneration. Towards this end we introduce in the solar cycle model of Lemerle & Charbonneau (2017. ApJ 834: 133) a magnetic flux-dependent variation of the surface meridional flow based on the axisymmetric inflow parameterization developped by Jiang et al. (2010. ApJ 717: 597). The inflow dependence on emerging magnetic flux thus introduces a bona fide nonlinear backreaction mechanism in the dynamo loop. For solar-like inflow speeds, our simulation results indicate a decrease of 10–20% in the strength of the global dipole building up at the end of an activity cycle, in agreement with earlier simulations based on linear surface flux transport models. Our simulations also indicate a significant stabilizing effect on cycle characteristics, in that individual cycle amplitudes in simulations including inflows show less scatter about their mean than in the absence of inflows. Our simulations also demonstrate an enhancement of cross-hemispheric coupling, leading to a significant decrease in hemispheric cycle amplitude asymmetries and temporal lag in hemispheric cycle onset. Analysis of temporally extended simulations also indicate that the presence of inflows increases the probability of cycle shutdown following an unfavorable sequence of emergence events. This results ultimately from the lower threshold nonlinearity built into our solar cycle model, and presumably operating in the sun as well.

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Climatology of Ionospheric Amplitude Scintillation on GNSS Signals at South American Sector During Solar Cycle 24

10.21203/rs.3.rs-411913/v1 ◽

2021 ◽

Author(s):

Eduardo Perez Macho ◽

Emilia Correia ◽

Luca Spogli ◽

Marcio Tadeu de Assis Honorato Muella

Keyword(s):

Solar Cycle ◽

Geomagnetic Storms ◽

Satellite System ◽

Scintillation Index ◽

Ionospheric Scintillation ◽

South American ◽

Amplitude Scintillation ◽

Solar Cycle 24 ◽

Cycle 24 ◽

The Impact

Abstract Scintillations are caused by ionospheric irregularities and can affect the propagation of trans-ionospheric radio signals. One way to understand and predict the impact of such irregularities on Global Navigation Satellite System (GNSS) signals is through the climatological behavior of the ionospheric scintillation indexes during the different phases of a solar cycle. In this work, we investigate the amplitude scintillation index S4 during the full solar cycle 24 at South American (SA) sector, that is featured by the Ionospheric Anomaly (EIA) and by the South Atlantic Magnetic Anomaly (SAMA). We also investigate the daily variation of S4 and two case studies during geomagnetic storms. The results show a significant intensification of amplitude scintillations at northern and southern crest of EIA, especially during the southern hemisphere’s spring/summer seasons, with a higher increase during solar maximum, and after sunset. And particularly at the SAMA region, where the intensity of magnetic field lines is lower, the S4 fluctuations are much higher.

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The Impact of Sunspots Number on Critical Frequencies foF2 for the IONOSPHERIC Layer-F2 Over Erbil Station During the Down Phase of Solar Cycle 24

NeuroQuantology ◽

10.14704/nq.2021.19.8.nq21128 ◽

2021 ◽

Vol 19 (8) ◽

pp. 157-168

Author(s):

Wafaa H.A. Zaki

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Sunspot Number ◽

Critical Frequency ◽

Radio Communication ◽

Ionospheric Layer ◽

Solar Cycle 24 ◽

Critical Frequency Fof2 ◽

Cycle 24 ◽

The Impact

The ionosphere layer (F2) is known as the most important layer for High frequency (Hf) radio communication because it is a permanent layer and excited during the day and night so it is able to reflect the frequencies at night and day due to its high critical frequency, and this layer is affected by daily and monthly solar activity. In this study the characteristics and behavior of F2 layer during Solar cycle 24 were studied, the effect of Sunspots number (Ri) on the critical frequency (foF2), were investigated for the years (2015, 2016, 2017, 2018, 2019, 2020) which represents the down phase of the solar cycle 24 over Erbil station (36° N, 44° E) by finding the critical frequency (foF2) values, the layer’ s impression times are determined for the days of solstice as well as equinox, where the solar activity was examined for the days of the winter and summer solstice and the days of the spring and autumn equinoxes for a period of 24 hours by applied the International Reference Ionosphere model IRI (2016). The output data for foF2 were verified by using the IRI-Ne- Quick option by specifying the time, date and Sunspot number parameters. Statistical analysis was caried out through the application of the Minitab (version 2018) in order to find the correlation between the critical frequency (foF2) of Ionospheric layer F2 and Sunspot number. It was concluded that the correlation is strong and positive, this indicate that critical frequency (foF2) increase with increasing Sunspots number (Ri) for solar cycle 24.

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Source-region characteristics of anemone active regions in the ascending phase of solar cycle 24

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038927 ◽

2020 ◽

Vol 642 ◽

pp. A233

Author(s):

R. Sharma ◽

C. Cid

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Minimum Distance ◽

Source Region ◽

Coronal Holes ◽

Active Regions ◽

Yearly Average ◽

Solar Cycle 24 ◽

Cycle 24 ◽

Rise Phase

Context. Active regions in close proximity to coronal holes, also known as anemone regions, are the best candidates for studying the interaction between closed and open magnetic field topologies at the Sun. Statistical investigation of their source-region characteristics can provide vital clues regarding their possible association with energetic events, relevant from space weather perspectives. Aims. The main goal of our study is to understand the distinct properties of flaring and non-flaring anemone active regions and their host coronal holes, by examining spatial and magnetic field distributions during the rise phase of the solar cycle, in the years 2011–2014. Methods. Anemone regions were identified from the minimum-distance threshold, estimated using the data available in the online catalogs for on-disk active regions and coronal holes. Along with the source-region area and magnetic field characteristics, associated filament and flare cases were also located. Regions with and without flare events were further selected for a detailed statistical examination to understand the major properties of the energetic events, both eruptive and confined, at the anemone-type active regions. Results. Identified anemone regions showed weak asymmetry in their spatial distribution over the solar disk, with yearly average independent from mean sunspot number trend, during the rise phase of solar cycle 24. With the progression in solar cycle, the area and minimum-distance parameters indicated a decreasing trend in their magnitudes, while the magnetic field characteristics indicated an increase in their estimated magnitudes. More than half of the regions in our database had an association with a filament structure, and nearly a third were linked with a magnetic reconnection (flare) event. Anemone regions with and without flares had clear distinctions in their source-region characteristics evident from the distribution of their properties and density analysis. The key differences included larger area and magnetic field magnitudes for flaring anemone regions, along with smaller distances between the centers of the active region and its host coronal hole.

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