J/other/SoPh/294.144 Coronal hole parameters (Heinemann+, 2019)
Statistical analysis and catalog of non-polar coronal holes covering the
SDO-era using CATCH,
Heinemann S.G., Temmer M., Heinemann N., Dissauer K., Samara E., Jercic V.,
Hofmeister S.J., Veronig A.M.
<Solar Physics, 294, 144 (2019)>
=2019SoPh..294..144H 2019SoPh..294..144H (SIMBAD/NED BibCode)
ADC_Keywords: Sun ; Magnetic fields ; Stars, atmospheres
Keywords: coronal holes - magnetic fields - photosphere - solar cycle -
observations - astrophysics - solar and stellar astrophysics
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 193Å
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
±60°, for which we derive sizes between 1.6x109 and
1.8x1011km2. The absolute value of the mean signed magnetic field
strength tends towards an average of 2.9±1.9G. 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.
Description:
Coronal hole parameters such as morphological properties, the
intensity, boundary stability as well as properties of the underlying
photospheric magnetic field and its fine structure are presented. 718
coronal holes between 2010 and 2019 have been extracted and analyzed
from 193A filtergrams taken by AIA/SDO. For each coronal hole the
following parameters are given (including uncertainties). Date,
Threshold, Category Factor, Area, Intensity (Mean + Median), Position,
Extension, Mean Magnetic Field Strength (Signed + Unsigned), Magnetic
Flux (Signed + Unsigned), Flux Balance, Skewness (Magnetic Field
Distribution), Flux Tube Number (Weak + Strong), Flux Tube Area Ratio
(Weak + Strong), Flux Tube Flux Ratio (Weak + Strong).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
params.dat 414 707 Coronal hole parameters
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See also:
III/238 : Synthetic spectra in the near-IR (Munari+, 2000-2001)
VI/138 : Sunspots catalogues, 1853-1870 (Casas+, 2013)
VI/152 : SOVAP-PICARD total solar irradiance (Meftah+, 2016)
J/other/SoPh/291.3527 : SOLAR/SOLSPEC UV SSI from 2008-2015 (Meftah+, 2016)
Byte-by-byte Description of file: params.dat
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Bytes Format Units Label Explanations
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1- 3 I03 --- CHNr Coronal Hole (CH) Number (CHNr)
5- 8 I04 yr Obs.Y Year of observation date (YYYY)
10- 11 I02 "month" Obs.M Month of observation date (MM)
13- 14 I02 d Obs.D Day of observation date (DD)
16- 17 I02 h Obs.h Hour of observation date (hh)
19- 20 I02 min Obs.m Minute of observation date (mm)
22- 23 I02 s Obs.s Second of observation date (ss)
25- 26 I02 --- Thr Intensity Thr in % I_med units (thr)
28- 33 F06.3 --- e_Thr Uncertainty in Thr in % I_med units (uthr)
35- 40 F06.3 --- Thrdn Intensity Thr in DN units (thrdn)
42- 47 F06.3 --- e_Thrdn Uncertainty in Thrdn in DN units(uthrdn)
49- 53 F05.3 --- CF Categroy Factor (cf)
55- 60 F06.3 10+10km+2 Area Coronal Hole Area (area)
62- 67 F06.3 10+10km+2 e_Area Uncertainty in Area (uarea)
69- 74 F06.3 --- meanInt Mean Coronal Hole Intensity in DN units
(meanint)
76- 81 F06.3 --- e_meanInt Uncertainty in meanInt in DN units
(umeanint)
83- 88 F06.3 --- meanInt50 Mean CH Intensity of the lowest 50%
in DN units (meanint50)
90- 95 F06.3 --- e_meanInt50 Uncertainty in meanInt50 in DN units
(umeanint50)
97-102 F06.3 --- meanInt25 Mean CH Intensity of the lowest 25%
in DN units (meanint25)
104-109 F06.3 --- e_meanInt25 Uncertainty in meanInt25 in DN units
(umeanint25)
111-116 F06.3 --- medInt Median Coronal Hole Intensity in DN units
in DN units (medint)
118-123 F06.3 --- e_medInt Uncertainty in medInt in DN units
(umedint)
125-130 F06.3 --- medInt50 Median CH Intensity of the lowest 50%
in DN units (medint50)
132-137 F06.3 --- e_medInt50 Uncertainty in medInt50 in DN units
(umedint50)
139-144 F06.3 --- medInt25 Median CH Intensity of the lowest 25%
in DN units (medint25)
146-151 F06.3 --- e_medInt25 Uncertaintys in medInt25 in DN units
(umedint25)
153-159 F07.3 deg comLON CH Center of Mass Longitude in HEEQ
(comlng)
161-167 F07.3 deg e_comLON Uncertainty in comLON (ucomlng)
169-175 F07.3 deg comLAT CH Center of Mass Latitude in HEEQ
(comlat)
177-183 F07.3 deg e_comLAT Uncertainty in comLAT (ucomlat)
185-191 F07.3 deg LONE Max Longitudinal Eastward Extent (HEEQ)
(lng_e)
193-199 F07.3 deg e_LONE Uncertainty in LONE (ulng_e)
201-207 F07.3 deg LONW Max Longitudinal Westward Extent (HEEQ)
(lng_w)
209-215 F07.3 deg e_LONW Uncertainty LONW (ulng_w)
217-223 F07.3 deg LATS Max Latitudinal Southward Extent (HEEQ)
(lat_s)
225-231 F07.3 deg e_LATS Uncertainty in LATS (ulat_s)
233-239 F07.3 deg LATN Max Latitudinal Northward Extent (HEEQ)
(lat_n)
241-247 F07.3 deg e_LATN Uncertainty in LATN (ulat_n)
249-255 F07.3 gauss magS Signed Mean Magnetic Field Strength
(mag_s)
257-263 F07.3 gauss e_magS Uncertainty in magS (umag_s)
265-270 F06.3 gauss magUS Unsigned Mean Magnetic Field Strength
(mag_us)
272-277 F06.3 gauss e_magUS Uncertainty in magUS (umag_us)
279-285 F07.3 --- fluxS Signed Magnetic Flux in 1020Mx units
(flux_s)
287-293 F07.3 --- e_fluxS Uncertainty in fluxS in 1020Mx units
(uflux_s)
295-301 F07.3 --- fluxUS Unsigned Magnetic Flux in 1020Mx units
(flux_us)
303-309 F07.3 --- e_fluxUS Uncertainty in fluxUS in 1020Mx units
(uflux_us)
311-316 F06.3 % fluxB Flux Balance (flux_b)
318-323 F06.3 % e_fluxB Uncertainty in fluxB (uflux_b)
325-331 F07.3 -- skew Skewness of the Magnetic Field (skew)
333-339 F07.3 -- e_skew Uncertainty in skew (uskew)
341-344 I04 -- ftnrW Number of Flux Tubes (Weak) (ftnr_w)
346-349 I04 -- e_ftnrW Uncertainty in ftnrW (uftnr_w)
351-353 I03 -- ftnrS Number of Flux Tubes (Strong) (ftnr_s)
355-357 I03 -- e_ftnrS ?=999 Uncertainty in ftnrS (uftnr_s)
359-364 F06.3 % ftarW Flux Tube Area Ratio (Weak) (ftar_w)
366-371 F06.3 % e_ftarW Uncertainty in ftarW (uftar_w)
373-378 F06.3 % ftarS Flux Tube Area Ratio (Strong) (ftar_s)
380-385 F06.3 % e_ftarS Uncertainty in ftarS (uftar_s)
387-392 F06.3 % ftfluxW Flux Tube Flux Ratio (Weak) (ftflux_w)
394-399 F06.3 % e_ftfluxW Uncertainty in ftfluxW (uftflux_w)
401-407 F07.3 % ftfluxS Flux Tube Flux Ratio (Strong) (ftflux_s)
409-414 F06.3 % e_ftfluxS ? Uncertainty ib ftfluxS (uftflux_s)
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Acknowledgements:
Stephan G. Heinemann, stephan.heinemann(at)hmail.at
(End) Stephan G. Heinemann [Univ. of Graz], Patricia Vannier [CDS] 06-Nov-2019