384 research outputs found
On-line Tools for Solar Data Compiled at the Debrecen Observatory and their Extensions with the Greenwich Sunspot Data
The primary task of the Debrecen Heliophysical Observatory (DHO) has been the
most detailed, reliable, and precise documentation of the solar photospheric
activity since 1958. This long-term effort resulted in various solar catalogs
based on ground-based and space-borne observations. A series of sunspot
databases and on-line tools were compiled at DHO: the Debrecen
Photoheliographic Data (DPD, 1974--), the dataset based on the Michelson
Doppler Imager (MDI) of the Solar and Heliospheric Observatory (SOHO) called
SOHO/MDI--Debrecen Data (SDD, 1996--2010), and the dataset based on the
Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO)
called SDO/HMI--Debrecen Data (HMIDD, 2010--). User-friendly web-presentations
and on-line tools were developed to visualize and search data. As a last step
of compilation, the revised version of Greenwich Photoheliographic Results
(GPR, 1874--1976) catalog was converted to DPD format, and a homogeneous
sunspot database covering more than 140 years was created. The database of
images for the GPR era was completed with the full-disc drawings of the
Hungarian historical observatories \'Ogyalla and Kalocsa (1872--1919) and with
the polarity drawings of Mount Wilson Observatory. We describe the main
characteristics of the available data and on-line tools.Comment: 25 pages, 11 figures, accepted for publication in Solar Physic
Active Longitude and Solar Flare Occurrences
The aim of the present work is to specify the spatio-temporal characteristics
of flare activity observed by the Reuven Ramaty High Energy Solar Spectroscopic
Imager (RHESSI) and Geostationary Operational Environmental Satellite (GOES)
satellites in connection with the behaviour of the longitudinal domain of
enhanced sunspot activity known as active longitude (AL). By using our method
developed for this purpose, we identified the AL in every Carrington Rotation
provided by the Debrecen Photoheliographic Data (DPD). The spatial probability
of flare occurrence has been estimated depending on the longitudinal distance
from AL in the northern and southern hemispheres separately. We have found that
more than the 60\% of the RHESSI and GOES flares is located within from the active longitude. Hence, the most flare-productive active
regions tend to be located in or close to the active longitudinal belt. This
observed feature may allow predicting the geo-effective position of the domain
of enhanced flaring probability. Furthermore, we studied the temporal
properties of flare occurrence near the active longitude and several
significant fluctuations were found. More precisely, the results of the method
are the following fluctuations: years, years and years. These
temporal and spatial properties of the solar flare occurrence within the active
longitudinal belts could provide us enhanced solar flare forecasting
opportunity
Statistical study of spatio-temporal distribution of precursor solar flares associated with major flares
The aim of the present investigation is to study the spatio-temporal
distribution of precursor flares during the 24-hour interval preceding M- and
X-class major flares and the evolution of follower flares. Information on
associated (precursor and follower) flares is provided by Reuven Ramaty High
Energy Solar Spectroscopic Imager (RHESSI). Flare List, while the major flares
are observed by the Geostationary Operational Environmental Satellite (GOES)
system satellites between 2002 and 2014. There are distinct evolutionary
differences between the spatio-temporal distributions of associated flares in
about one day period depending on the type of the main flare. The spatial
distribution was characterised by the normalised frequency distribution of the
quantity (the distance between the major flare and its precursor flare
normalised by the sunspot group diameter) in four 6-hour time intervals before
the major event. The precursors of X-class flares have a double-peaked spatial
distribution for more than half a day prior to the major flare, but it changes
to a lognormal-like distribution roughly 6 hours prior to the event. The
precursors of M-class flares show lognormal-like distribution in each 6-hour
subinterval. The most frequent sites of the precursors in the active region are
within a distance of about 0.1 diameter of sunspot group from the site of the
major flare in each case. Our investigation shows that the build-up of energy
is more effective than the release of energy because of precursors
Comparison of Debrecen and Mount Wilson/Kodaikanal sunspot group tilt angles and the Joy's law
The study of active region tilt angles and their variations in different time
scales plays an important role in revealing the subsurface dynamics of magnetic
flux ropes and in understanding the dynamo mechanism. In order to reveal the
exact characteristics of tilt angles, precise long-term tilt angle data bases
are needed. However, there are only a few different data sets at present, which
are difficult to be compared and cross-calibrate because of their substantial
deviations. In this paper, we describe new tilt angle data bases derived from
the Debrecen Photoheliographic Data () (1974--) and from the
SOHO/MDI-Debrecen Data () (1996-2010) sunspot catalogues. We compare them
with the traditional sunspot group tilt angle data bases of Mount Wilson
Observatory (1917-85) and Kodaikanal Solar Observatory (1906-87) and we analyse
the deviations. Various methods and filters are investigated which may improve
the sample of data and may help deriving better results based on combined data.
As a demonstration of the enhanced quality of the improved data set a refined
diagram of the Joy's law is presented.Comment: 10 pages, 12 figures, Accepted for publication in MNRA
Active-Region Tilt Angles: Magnetic Versus White-Light Determinations of Joy's Law
The axes of solar active regions are inclined relative to the east--west
direction, with the tilt angle tending to increase with latitude ("Joy's law").
Observational determinations of Joy's law have been based either on white-light
images of sunspot groups or on magnetograms, where the latter have the
advantage of measuring directly the physically relevant quantity (the
photospheric field), but the disadvantage of having been recorded routinely
only since the mid-1960s. White-light studies employing the historical Mount
Wilson (MW) database have yielded tilt angles that are smaller and that
increase less steeply with latitude than those obtained from magnetic data. We
confirm this effect by comparing sunspot-group tilt angles from the Debrecen
Photoheliographic Database with measurements made by Li and Ulrich using MW
magnetograms taken during cycles 21--23. Whether white-light or magnetic data
are employed, the median tilt angles significantly exceed the mean values, and
provide a better characterization of the observed distributions. The
discrepancy between the white-light and magnetic results is found to have two
main sources. First, a substantial fraction of the white-light "tilt angles"
refer to sunspots of the same polarity. Of greater physical significance is
that the magnetograph measurements include the contribution of plage areas,
which are invisible in white-light images but tend to have greater axial
inclinations than the adjacent sunspots. Given the large uncertainties inherent
in both the white-light and the magnetic measurements, it remains unclear
whether any systematic relationship exists between tilt angle and cycle
amplitude during cycles 16--23.Comment: 35 pages, 13 figures, Accepted in Ap
Research for policy influence : a history of IDRC intent
Part of the collection of government and miscellaneous documents relating to the history of IDRC.This paper tells the story of how the Centre's intent on linking research and policy processes has evolved over the years. There has been a persistent concern with the use of research over three decades of IDRC’s history. The task of refining a corporate strategy to foster research for policy change, and especially of putting it into practice, remains a work in progress. This study is based on analysis of IDRC planning documents, reports, internal papers, evaluations and reviews, as well as selected Board minutes. External documents were also consulted to help provide context
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