@article{aruliah1996,
author = {Aruliah, A.L. and Farmer, A.D. and Fuller-Rowell, T.J. and
Wild, M.N. and Hapgood, M. and Rees, D.},
title = {An equinoctial asymmetry in the high-latitude thermosphere
and ionosphere},
journal = {Journal of Geophysical Research},
pages = {15713--15722},
year = {1996},
month = jul,
volume = {101},
number = {A7},
abstract = {A large equinoctial asymmetry has been observed in
thermospheric winds and ion velocities at high latitude
sites in northern Scandinavia. Throughout the solar cycle,
average nighttime thermospheric meridional winds are larger
in spring than autumn despite similar levels of solar
insolation. The average ion velocities are also larger in
spring than autumn at solar maximum, but at solar minimum
this position is reversed. Numerical simulations of the
thermosphere and ionosphere have not predicted such
asymmetries because they generally assume forcing functions
that are symmetric about the solstices. The proposed
explanation lies in the annual and diurnal variation in
solar wind-magnetosphere coupling caused by changes in the
orientation of the geomagnetic pole, and hence the
magnetosphere, with respect to the average orientation of
the IMF (the Russell-McPherron effect). This causes a
12-hour phase difference between the times of maximum solar
wind-magnetosphere coupling at the two equinoxes. In
addition, the orientation of the geomagnetic axis with
respect to the average IMF is such that $ > 0$
for the March equinox and $ < 0$ for
September. This results in a further source of asymmetry of
forcing of the high-latitude ionosphere as the result of
electric fields associated with the four sign combinations
of $B_{y}$ and $B_{z}$. Several predictions arise from the
explanation given: for example, a high-latitude station
measuring thermospheric neutral winds in Alaska,
$180^{\circ}$ in longitude from Kiruna, might be expected to
see nighttime thermospheric winds that are larger in the
autumn than in the spring.},
url = {http://www.agu.org/pubs/crossref/1996/95JA01102.shtml},
ukssdc_w = {}
}
@article{aruliah97:_model_high_latit_equin_asymm,
author = {Aruliah, A.L. and Schoendorf, J. and Aylward, A.D. and Wild,
M.N.},
title = {Modelling the High-Latitude Equinoctial Asymmetry},
journal = {Journal of Geophysical Research},
pages = {27207--27216},
year = {1997},
volume = {102},
number = {A12},
abstract = {Fabry-Perot Interferometer measurements of neutral winds and
European Incoherent SCATter radar measurements of plasma
velocities have shown a significant equinoctial asymmetry in
the average behavior of the thermosphere and ionosphere
above northern Scandinavia. Existing standard models of the
upper atmosphere use forcing functions that are symmetric
about the solstices, therefore these observations are
unexpected. It is suggested that the asymmetry arises from
the diurnal variation in the cross polar cap potential
difference (CPCPD) because there is a 12 hour phase
difference between the variations at the March and September
equinoxes. The variation in the CPCPD is caused by an annual
and diurnal variation in the orientation of the
magnetosphere with respect to the interplanetary magnetic
field. This is known as the Russell-McPherron(R-M)
effect. The plausibility of this explanation of the
equinoctial asymmetry in thermospheric winds is supported by
investigation of the effect of their geomagnetic history,
i.e., the repercussions on the winds of the activity levels
in the few hours prior to the observation. The consequences
of the R-M effect have been simulated in the University
College London/Sheffield/Space Environment Laboratory
coupled thermosphere-ionosphere model by imposing a
diurnally varying high-latitude electric field pattern. The
results are used to test the predictions, given in an
earlier paper, of the average behavior expected at other
high-latitude sites. A corollary to the study is that the
evidence presented here implies that the auroral oval may be
smaller at solar minimum, which is also unexpected.},
ukssdc_w = {}
}
@article{willis13:_green_photo_resul_B,
author = {D. M. Willis and R. Henwood and M.N. Wild and H.E. Coffey
and W.F. Denig and E.H. Erwin and D. V. Hoyt},
title = {The Greenwich Photo-heliographic Results (1874--1976):
Procedures for Checking and Correcting the Sunspot Digital
Datasets},
journal = {Solar Physics},
year = 2013,
abstract = {Attention is drawn to the existence of errors in the
original digital dataset containing sunspot data extracted
from certain sections of the printed Greenwich
Photo-heliographic Results (GPR) 1874--1976. Calculating
the polar coordinates from the heliographic coordinates and
comparing them with the recorded polar coordinates reveals
that there are both isolated and systematic errors in the
original sunspot digital dataset, particularly during the
early years (1874--1914). It should be noted that most of
these errors are present in the compiled sunspot digital
dataset and not in the original printed copies of the
Greenwich Photo-heliographic Results. Surprisingly, many of
the errors in the digitised positions of sunspot groups are
apparently in the measured polar coordinates, not the
derived heliographic coordinates. The mathematical equations
that are used to convert between heliographic and polar
coordinate systems are formulated and then used to calculate
revised (digitised) polar coordinates for sunspot groups, on
the assumption that the heliographic coordinates of every
sunspot group are correct. The additional complication of
requiring accurate solar ephemerides in order to solve the
mathematical equations is discussed in detail. It is shown
that the isolated and systematic errors, which are prevalent
in the sunspot digital dataset during the early years,
disappear if revised polar coordinates are used instead. A
comprehensive procedure for checking the original sunspot
digital dataset is formulated in an Appendix.},
doi = {10.1007/s11207-013-0312-x},
url = {http://link.springer.com/article/10.1007/s11207-013-0312-x},
ukssdc_w = {}
}
@article{willis13:_green_photo_resul_A,
author = {D.M. Willis and H.E. Coffey and R. Henwood and E.H. Erwin
and D.V. Hoyt and M.N. Wild and W.F. Denig},
title = {The Greenwich Photo-heliographic Results (1874--1976):
Summary of the Observations, Applications, Datasets,
Definitions and Errors},
journal = {Solar Physics},
year = 2013,
abstract = {The measurements of sunspot positions and areas that were
published initially by the Royal Observatory, Greenwich, and
subsequently by the Royal Greenwich Observatory (RGO), as
the Greenwich Photo-heliographic Results (GPR), 1874--1976,
exist in both printed and digital forms. These printed and
digital sunspot datasets have been archived in various
libraries and data centres. Unfortunately, however,
typographic, systematic and isolated errors can be found in
the various datasets. The purpose of the present paper is to
begin the task of identifying and correcting these
errors. In particular, the intention is to provide in one
foundational paper all the necessary background information
on the original solar observations, their various
applications in scientific research, the format of the
different digital datasets, the necessary definitions of the
quantities measured, and the initial identification of
errors in both the printed publications and the digital
datasets. Two companion papers address the question of
specific identifiable errors; namely, typographic errors in
the printed publications, and both isolated and systematic
errors in the digital datasets. The existence of two
independently prepared digital datasets, which both contain
information on sunspot positions and areas, makes it
possible to outline a preliminary strategy for the
development of an even more accurate digital
dataset. Further work is in progress to generate an
extremely reliable sunspot digital dataset, based on the
programme of solar observations supported for more than a
century by the Royal Observatory, Greenwich, and the Royal
Greenwich Observatory. This improved dataset should be of
value in many future scientific investigations.},
doi = {10.1007/s11207-013-0311-y},
url = {http://link.springer.com/article/10.1007/s11207-013-0311-y},
ukssdc_w = {}
}
@article{davis1997,
author = {Davis, C. J. and Wild, M. N. and Lockwood, M. and Tulunay,
Y. K.},
affiliation = {Rutherford Appletpn Laboratory Chilton Didcot OX11 OQX
United Kingdom},
title = {Ionospheric and geomagnetic responses to changes in {IMF}
${B}_{z}$: a superposed epoch study},
journal = {Annales Geophysicae},
publisher = {Springer Berlin / Heidelberg},
issn = {0992-7689},
keyword = {Earth and Environmental Science},
pages = {217-230},
volume = 15,
issue = 2,
url = {http://dx.doi.org/10.1007/s00585-997-0217-9},
doi = {10.1007/s00585-997-0217-9},
abstract = {Superposed epoch studies have been carried out in order to
determine the ionospheric response at mid-latitudes to
southward turnings of the interplanetary magnetic field
(IMF). This is compared with the geomagnetic response, as
seen in the indices ${K}_{p}$, ${AE}$ and $Dst$. The solar
wind, IMF and geomagnetic data used were hourly averages
from the years 1967--1989 and thus cover a full 22-year
cycle in the solar magnetic field. These data were divided
into subsets, determined by the magnitudes of the southward
turnings and the concomitant increase in solar wind
pressure. The superposed epoch studies were carried out
using the time of the southward turning as time zero. The
response of the mid-latitude ionosphere is studied by
looking at the F-layer critical frequencies, $f_{o}F2$, from
hourly soundings by the Slough ionosonde and their deviation
from the monthly median values, ${\delta}f_{o}F2$. For the
southward turnings with a change in $B_{z}$ of
${\delta}B_{z}>11.5$ nT accompanied by a solar wind dynamic
pressure $P$ exceeding 5 nPa, the F region critical
frequency, $f_{o}F2$, shows a marked decrease, reaching a
minimum value about 20 h after the southward turning. This
recovers to pre-event values over the subsequent 24 h, on
average. The $Dst$ index shows the classic storm-time
decrease to about -60 nT. Four days later, the index has
still to fully recover and is at about -25 nT. Both the
$K_{p}$ and $AE$ indices show rises before the southward
turnings, when the IMF is strongly northward but the solar
wind dynamic pressure is enhanced. The average $AE$ index
does register a clear isolated pulse (averaging 650 nT for 2
h, compared with a background peak level of near 450 nT at
these times) showing enhanced energy deposition at high
latitudes in substorms but, like $K_{p}$, remains somewhat
enhanced for several days, even after the average IMF has
returned to zero after 1 day. This $AE$ background decays
away over several days as the $Dst$ index recovers,
indicating that there is some contamination of the currents
observed at the $AE$ stations by the continuing enhanced
equatorial ring current. For data averaged over all seasons,
the critical frequencies are depressed at Slough by 1.3 MHz,
which is close to the lower decile of the overall
distribution of ${\delta}f_{o}F2$ values. Taking 30-day
periods around summer and winter solstice, the largest
depression is 1.6 and 1.2 MHz, respectively. This seasonal
dependence is confirmed by a similar study for a Southern
Hemisphere station, Argentine Island, giving peak
depressions of 1.8 MHz and 0.5 MHz for summer and
winter. For the subset of turnings where
${\delta}B_{z}>11.5$ nT and $P<= 5$ nPa, the response of the
geomagnetic indices is similar but smaller, while the change
in ${\delta}f_{o}F2$ has all but disappeared. This confirms
that the energy deposited at high latitudes, which leads to
the geomagnetic and ionospheric disturbances following a
southward turning of the IMF, increases with the energy
density (dynamic pressure) of the solar wind flow. The
magnitude of all responses are shown to depend on
${\delta}B_{z}$. At Slough, the peak depression always
occurs when Slough rotates into the noon sector. The largest
ionospheric response is for southward turnings seen between
15--21 UT.},
ukssdc_w = {},
pdf = {http://www.ann-geophys.net/15/217/1997/angeo-15-217-1997.pdf},
year = 1997
}
@article{willis13:_green_photo_resul_C,
author = {E.H. Erwin and H.E. Coffey and W.F. Denig and D.M. Willis
and R. Henwood and M.N. Wild},
title = {The Greenwich Photo-heliographic Results (1874--1976):
Initial Corrections to the Printed Publications},
journal = {Solar Physics},
year = {2013},
abstract = {A new sunspot and faculae digital dataset for the interval
1874--1955 has been prepared under the auspices of the NOAA
National Geophysical Data Center (NGDC). This digital
dataset contains measurements of the positions and areas of
both sunspots and faculae published initially by the Royal
Observatory, Greenwich, and subsequently by the Royal
Greenwich Observatory (RGO), under the title Greenwich
Photo-heliographic Results (GPR), 1874--1976. Quality
control (QC) procedures based on logical consistency have
been used to identify the more obvious errors in the RGO
publications. Typical examples of identifiable errors are
North versus South errors in specifying heliographic
latitude, errors in specifying heliographic (Carrington)
longitude, errors in the dates and times, errors in sunspot
group numbers, arithmetic errors in the summation process,
and the occasional omission of solar ephemerides. Although
the number of errors in the RGO publications is remarkably
small, an initial table of necessary corrections is provided
for the interval 1874--1917. Moreover, as noted in the
preceding companion papers, the existence of two
independently prepared digital datasets, which both contain
information on sunspot positions and areas, makes it
possible to outline a preliminary strategy for the
development of an even more accurate digital
dataset. Further work is in progress to generate an
extremely reliable sunspot digital dataset, based on the
long programme of solar observations supported first by the
Royal Observatory, Greenwich, and then by the Royal
Greenwich Observatory.},
doi = {10.1007/s11207-013-0310-z},
url = {http://link.springer.com/article/10.1007/s11207-013-0310-z},
ukssdc_w = {}
}
@incollection{hapgood1993,
author = {Hapgood, M.A.},
editor = {Heck, A. and Murtagh, F.},
title = {Multi-step queries: the need for a correlation environment},
booktitle = {Adding Intelligence to Information Retrieval: the Case of
Astronomy and Related Space Sciences},
year = {1993},
month = jan,
publisher = {Kluwer},
address = {Dordrecht},
ukssdc_w = {}
}
@article{hapgood1991,
author = {Hapgood, M.A. and Lockwood, M. and Bowe, G.A. and Willis,
D.M. and Tulunay, Y.K.},
title = {Variability of the interplanetary medium at 1 a.u. over 24
years: 1963--1986},
journal = {Planetary and Space Science},
pages = {411--423},
year = {1991},
month = mar,
volume = {39},
number = {3},
abstract = {A survey is presented of hourly averages of observations of
the interplanetary medium, made by satellites close to the
Earth (i.e. at 1 a.u.) in the years 1963-1986. This survey
therefore covers two complete solar cycles (numbers 20 and
21). The distributions and solar-cycle variations of IMF
field strength, $B$, and its northward component (in GSM
coordinates), $B_{z}$, and of the solar-wind density, n,
speed, $\upsilon$, and dynamic pressure, P, are
discussed. Because of their importance to the terrestrial
magnetosphere/ionosphere, particular attention is given to
$B_{z}$ and P. The solar-cycle variation in the magnitude
and variability of $B_{z}$, previously reported for cycle
20, is also found for cycle 21. However, the solar-wind data
show a number of differences between cycles 20 and 21. The
average dynamic pressure is found to show a solar-cycle
variation and a systematic increase over the period of the
survey. The minimum of dynamic pressure at sunspot maximum
is mainly due to reduced solar-wind densities in cycle 20,
but lower solar-wind speed in cycle 21 is a more significant
factor. The distribution of the duration of periods of
stable polarity of the IMF $B_{z}$ component shows that the
magnetosphere could achieve steady state for only a small
fraction of the time and there is some evidence for a
solar-cycle variation in this fraction. It is also found
that the polarity changes in the IMF $B_{z}$ fall into two
classes: one with an associated change in solar-wind dynamic
pressure, the other without such a change. However, in only
20\% of cases does the dynamic pressure change exceed 50\%.},
ukssdc_w = {}
}
@techreport{rs1982,
author = {Hewish, A. and others},
title = {Synoptic data for Solar-Terrestrial Monitoring},
institution = {The Royal Society},
year = {1992},
month = sep,
address = {London},
ukssdc_w = {}
}
@article{0004-637X-862-1-15,
author = {Hisashi Hayakawa and Yusuke Ebihara and David M. Willis and
Kentaro Hattori and Alessandra S. Giunta and Matthew N.
Wild and Satoshi Hayakawa and Shin Toriumi and Yasuyuki
Mitsuma and Lee T. Macdonald and Kazunari Shibata and Sam
M. Silverman},
title = {The Great Space Weather Event during 1872 February Recorded
in East Asia},
journal = {The Astrophysical Journal},
volume = 862,
number = 1,
pages = 15,
url = {http://stacks.iop.org/0004-637X/862/i=1/a=15},
doi = {10.3847/1538-4357/aaca40},
year = 2018,
abstract = {The study of historical great geomagnetic storms is crucial
for assessing the possible risks to the technological
infrastructure of a modern society, caused by extreme
space-weather events. The normal benchmark has been the
great geomagnetic storm of 1859 September, the so-called
''Carrington Event.'' However, there are numerous records of
another great geomagnetic storm in 1872 February. This
storm, which occurred about 12 years after the Carrington
Event, resulted in comparable magnetic disturbances and
auroral displays over large areas of the Earth. We have
revisited this great geomagnetic storm in terms of the
auroral and sunspot records in historical documents from
East Asia. In particular, we have surveyed the auroral
records from East Asia and estimated the equatorward
boundary of the auroral oval to be near $24.2^{\circ}$ invariant
latitude, on the basis that the aurora was seen near the
zenith at Shanghai ($20^{\circ}$ magnetic latitude, MLAT). These
results confirm that this geomagnetic storm of 1872 February
was as extreme as the Carrington Event, at least in terms of
the equatorward motion of the auroral oval. Indeed, our
results support the interpretation of the simultaneous
auroral observations made at Bombay ($10^{\circ}$ MLAT). The East
Asian auroral records have indicated extreme brightness,
suggesting unusual precipitation of high-intensity,
low-energy electrons during this geomagnetic storm. We have
compared the duration of the East Asian auroral displays
with magnetic observations in Bombay and found that the
auroral displays occurred in the initial phase, main phase,
and early recovery phase of the magnetic storm.},
ukssdc_w = {}
}
@article{king1973,
author = {King, J.W.},
title = {Solar radiation changes and the weather},
journal = {Nature},
pages = {443--446},
year = {1973},
month = oct,
volume = {245},
ukssdc_w = {}
}
@article{liu1983,
author = {Liu, C. and Smith, P.A. and King, J.W.},
title = {A new solar index which leads to improved foF2 predictions
using the CCIR Atlas},
journal = {Telecommunications Journal},
pages = {408--414},
year = {1983},
volume = {50},
number = {VIII},
ukssdc_w = {}
}
@article{2006JGRA..11109109L,
author = {Lockwood, M. and Rouillard, A.P. and Finch, I. and Stamper,
R.},
title = {{Comment on ``The IDV index: Its derivation and use in
inferring long-term variations of the interplanetary
magnetic field strength'' by Leif Svalgaard and Edward
W. Cliver}},
journal = {Journal of Geophysical Research (Space Physics)},
year = 2006,
month = sep,
volume = 111,
number = {A10},
pages = {9109-+},
doi = {10.1029/2006JA011640},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRA..11109109L},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_w = {}
}
@article{lockwood1999,
author = {Lockwood, M. and Stamper, R.},
title = {Long-term drift of the coronal source magnetic flux and the
total solar irradiance},
journal = {Geophysical Research Letters},
pages = {2461-2464},
year = 1999,
month = {august},
volume = 26,
number = 16,
ukssdc_w = {},
abstract = {We test the method of Lockwood et al. [1999] for deriving
the coronal source flux from the geomagnetic aa index and
show it to be accurate to within 12\% for annual means and
4.5\% for averages over a sunspot cycle. Using data from
four solar constant monitors during 1981--1995, we find a
linear relationship between this magnetic flux and the total
solar irradiance. From this correlation, we show that the
131\% rise in the mean coronal source field over the
interval 1901--1995 corresponds to a rise in the average
total solar irradiance of $\Delta I = 1.65 \pm 0.23
Wm^{-2}$.},
url = {grlcover.html}
}
@article{lockwood1999:_doubling_coronal_mag_field,
author = {Lockwood, M. and Stamper, R. and Wild, M.},
title = {A Doubling of the Sun's Coronal Magnetic Field during the
Last 100 Years},
journal = {Nature},
volume = 399,
pages = {437--439},
year = 1999,
month = {june},
abstract = {The solar wind is an extended ionized gas of very high
electrical conductivity, and therefore drags some magnetic
flux out of the Sun to fill the heliosphere with a weak
interplanetary magnetic field,. Magnetic reconnection -- the
merging of oppositely directed magnetic fields -- between
the interplanetary field and the Earth's magnetic field
allows energy from the solar wind to enter the near-Earth
environment. The Sun's properties, such as its luminosity,
are related to its magnetic field, although the connections
are still not well understood,. Moreover, changes in the
heliospheric magnetic field have been linked with changes in
total cloud cover over the Earth, which may influence global
climate. Here we show that measurements of the near-Earth
interplanetary magnetic field reveal that the total magnetic
flux leaving the Sun has risen by a factor of 1.4 since
1964: surrogate measurements of the interplanetary magnetic
field indicate that the increase since 1901 has been by a
factor of 2.3. This increase may be related to chaotic
changes in the dynamo that generates the solar magnetic
field. We do not yet know quantitatively how such changes
will influence the global environment.},
ukssdc_w = {},
pdf = {http://www.nature.com/nature/journal/v399/n6735/pdf/399437a0.pdf},
url = {http://www.nature.com/nature/journal/v399/n6735/abs/399437a0.html},
doi = {10.1038/20867}
}
@techreport{lockwood95:_groun_based_measur_suppor_clust,
author = {Lockwood, M. and Stamper, R. and Wild, M.N. and Opgenoorth,
H.J.},
title = {Ground-Based Measurements in Support of CLUSTER: An On-Line
Planning Procedure},
institution = {DRAL},
year = {1995},
month = feb,
number = {RAL-95-018},
ukssdc_w = {}
}
@article{lockwood99:_onset_expan_enhan_ionos_convec,
author = {Lockwood, M. and Wild, M.N. and Cowley, S.W.H.},
title = {The Onset and Expansion of Enhanced Ionospheric Convection
Following a Southward Turning of the IMF},
journal = {Journal of Geophysical Research},
year = {1999},
note = {submitted},
ukssdc_w = {}
}
@inproceedings{lockwood99:_predic,
author = {Lockwood, M. and Wild, M.N. and Stamper, R. and Grande, M.},
title = {Predicting solar disturbance effects on navigation systems},
booktitle = {Journal of Navigation},
pages = {203--216},
year = {1999},
volume = {52},
ukssdc_w = {}
}
@incollection{opgenoorth97:_new_famil_geomag_distur_indic,
author = {Opgenoorth, H.J. and Persson, M.A.L. and Lockwood, M. and
Stamper, R. and Wild, M.N. and Pellinen, R. and Pulkkinen,
T. and Kauristie, K. and Hughes, T. and Kamide, Y.},
editor = {Lockwood, M. and Wild, M.N. and Opgenoorth, H.J.},
title = {A New Family of Geomagnetic Disturbance Indices},
booktitle = {Satellite - Ground Based Coordination Sourcebook},
pages = {49--62},
year = {1997},
publisher = {ESA},
volume = {SP-1198},
ukssdc_w = {}
}
@article{pulkkinen01:_sun_g_connec_time_scales,
author = {Pulkkinen, T.I. and Nevanlinna, H. and Pulkkinen, P.J. and
Lockwood M.},
title = {The Sun-Earth Connection in Time Scales from Years to Decades and Centuries},
journal = {Space Science Reviews},
year = 2001,
volume = 95,
number = {1-2},
pages = {625--637},
month = jan,
ukssdc_w = {},
abstract = {The Sun--Earth connection is studied using long-term
measurements from the Sun and from the Earth. The auroral
activity is shown to correlate to high accuracy with the
smoothed sunspot numbers. Similarly, both geomagnetic
activity and global surface temperature anomaly can be
linked to cyclic changes in the solar activity. The
interlinked variations in the solar magnetic activity and in
the solar irradiance cause effects that can be observed both
in the Earth's biosphere and in the electromagnetic
environment. The long-term data sets suggest that the
increase in geomagnetic activity and surface temperatures
are related (at least partially) to longer-term solar
variations, which probably include an increasing trend
superposed with a cyclic behavior with a period of about 90
years.}
}
@unpublished{saunders1993,
author = {Saunders, M.A. and Lockwood, M. and Wild, M.N.},
title = {The semi-annual variation in great geomagnetic storms},
year = {1993},
month = mar,
note = {Submitted to Annales Geophysicae},
ukssdc_w = {}
}
@article{stamper1996,
author = {Stamper, R.},
title = {Improved prediction of I_{F2} and I_{G} indices using neural
networks},
journal = {IEEE Proc.-Microw. Antennas Propag.},
pages = {341--346},
year = {1996},
month = aug,
volume = {143},
number = {4},
ukssdc_w = {}
}
@article{stamper98:_solar_causes_long_term_increas_geomag_activ,
author = {Stamper, R. and Lockwood, M. and Wild, M.N. and Clark,
T.D.G.},
title = {Solar Causes of the Long-Term Increase in Geomagnetic
Activity},
journal = {Journal of Geophysical Research},
pages = {28325--28342},
year = {1999},
month = dec,
volume = {104},
number = {A12},
ukssdc_w = {},
abstract = {We analyze the causes of the century-long increase in
geomagnetic activity, quantified by annual means of the {\it
aa} index, using observations of interplanetary space,
galactic cosmic rays, the ionosphere, and the auroral
electrojet, made during the last three solar cycles. The
effects of changes in ionospheric conductivity, the Earth's
dipole tilt, and magnetic moment are shown to be small; only
changes in near-Earth interplanetary space make a
significant contribution to the long-term increase in
activity. We study the effects of the interplanetary medium
by applying dimensional analysis to generate the optimum
solar wind-magnetosphere energy coupling function, having an
unprecedentedly high correlation coefficient of
0.97. Analysis of the terms of the coupling function shows
that the largest contributions to the drift in activity over
solar cycles 20--22 originate from rises in the average
interplanetary magnetic field (IMF) strength, solar wind
concentration, and speed; average IMF orientation has grown
somewhat less propitious for causing geomagnetic
activity. The combination of these factors explains almost
all of the 39\% rise in {\it aa} observed over the last
three solar cycles. Whereas the IMF strength varies
approximately in phase with sunspot numbers, neither its
orientation nor the solar wind density shows any coherent
solar cycle variation. The solar wind speed peaks strongly
in the declining phase of even-numbered cycles and can be
identified as the chief cause of the phase shift between the
sunspot numbers and the {\it aa} index. The rise in the IMF
magnitude, the largest single contributor to the drift in
geomagnetic activity, is shown to be caused by a rise in the
solar coronal magnetic field, consistent with a rise in the
coronal source field, modeled from photospheric
observations, and an observed decay in cosmic ray fluxes.}
}
@incollection{stamper97:_on_line_direc_groun_based_stp_obser,
author = {Stamper, R. and Wild, M. and Lockwood, M.},
editor = {Lockwood, M. and Wild, M.N. and Opgenoorth, H.J.},
title = {An On-Line Directory of Ground-Based STP Observatories},
booktitle = {Satellite - Ground Based Coordination Sourcebook},
pages = {367--407},
year = {1997},
publisher = {ESA},
volume = {SP-1198},
ukssdc_w = {}
}
@article{szuszczewicz1997,
author = {Szuszczewicz, E.P. and Blanchard, P. and Wilkinson, P. and
Crowley, G. and Fuller-Rowell, T. and Richards, P. and Abdu,
M. and Bullett, T. and Hanbaba, R. and Lebreton, J.P. and
Lester, M. and Lockwood, M. and Millward, G. and Wild,
M. and Pulinets, S. and Reddy, B.M. and Stanislawska, I. and
Vannaroni, G. and Zolesi, B.},
title = {The First Realtime Worldwide Ionospheric Prediction Network:
An Advance in Support of Spaceborne Experimentation, On-Line
Model Validation, and Space Weather},
journal = {Geophysical Research Letters},
pages = {449-452},
year = {1998},
month = {feb},
volume = {25},
number = {4},
abstract = {We report on the first realtime ionospheric predictions
network and its capabilities to ingest a global database and
forecast F-layer characteristics and ``in situ'' electron
densities along the track of an orbiting spacecraft. A
global network of ionosonde stations reported
around-the-clock observations of F-region heights and
densities, and an on-line library of models provided
forecasting capabilities. Each model was tested against the
incoming data; relative accuracies were intercompared to
determine the best overall fit to the prevailing conditions;
and the best-fit model was used to predict ionospheric
conditions on an orbit-to-orbit basis for the 12-hour period
following a twice-daily model test and validation
procedure. It was found that the best-fit model often
provided averaged (i.e., climatologically-based) accuracies
better than 5\% in predicting the heights and critical
frequencies of the F-region peaks in the latitudinal domain
of the TSS-1R flight path. There was a sharp contrast,
however, in model-measurement comparisons involving
predictions of actual, unaveraged, along-track densities at
the 295 km orbital altitude of TSS-1R. In this case, extrema
in the first-principle models varied by as much as an order
of magnitude in density predictions, and the best-fit models
were found to disagree with the ``in situ'' observations of
Ne by as much as 140\%. The discrepancies are interpreted as
a manifestation of difficulties in accurately and
self-consistently modeling the external controls of solar
and magnetospheric inputs and the spatial and temporal
variabilities in electric fields, thermospheric winds,
plasmaspheric fluxes, and chemistry.},
ukssdc_w = {}
}
@incollection{wild97:_clust_groun_based_data_centr,
author = {Wild, M.N. and Lockwood, M.},
editor = {Lockwood, M. and Wild, M.N. and Opgenoorth, H.J.},
title = {Cluster-Ground Based Data Centre},
booktitle = {Satellite - Ground Based Coordination Sourcebook},
pages = {361--366},
year = {1997},
publisher = {ESA},
volume = {SP-1198},
ukssdc_w = {}
}
@article{Willis2016b,
author = {Willis, D. M. and Wild, M. N. and Appleby, G. M. and
Macdonald, L. T.},
title = {The Greenwich Photo-heliographic Results
(1874{\thinspace}--{\thinspace}1885): Observing Telescopes,
Photographic Processes, and Solar Images},
journal = {Solar Physics},
year = {2016},
pages = {1--34},
abstract = {Potential sources of inhomogeneity in the sunspot
measurements published by the Royal Observatory, Greenwich,
during the early interval 1874{\thinspace}--{\thinspace}1885
are examined critically. Particular attention is paid to
inhomogeneities that might arise because the sunspot
measurements were derived from solar photographs taken at
various contributing solar observatories, which used
different telescopes, experienced different seeing
conditions, and employed different photographic
processes. The procedures employed in the Solar Department
at the Royal Greenwich Observatory (RGO), Herstmonceux,
during the final phase of sunspot observations provide a
modern benchmark for interpreting the early sunspot
measurements. The different observing telescopes used at the
contributing solar observatories during the interval
1874{\thinspace}--{\thinspace}1885 are discussed in detail,
using information gleaned from the official RGO publications
and other relevant historical documents. Likewise, the
different photographic processes employed at the different
solar observatories are reviewed carefully. The procedures
used by RGO staff to measure the positions and areas of
sunspot groups on photographs of the Sun having a nominal
radius of either four or eight inches are described. It is
argued that the learning curve for the use of the Kew
photoheliograph at the Royal Observatory, Greenwich,
actually commenced in 1858, not 1874. The RGO daily number
of sunspot groups is plotted graphically and analysed
statistically. Similarly, the changes of metadata at each
solar observatory are shown on the graphical plots and
analysed statistically. It is concluded that neither the
interleaving of data from the different solar observatories
nor the changes in metadata invalidates the RGO count of the
number of sunspot groups, which behaves as a
quasi-homogeneous time series. Furthermore, it is emphasised
that the correct treatment of days without photographs is
quite crucial to the correct calculation of Group Sunspot
Numbers.},
issn = {1573-093X},
doi = {10.1007/s11207-016-0894-1},
url = {http://dx.doi.org/10.1007/s11207-016-0894-1},
pdf = {http://link.springer.com/content/pdf/10.1007%2Fs11207-016-0894-1.pdf},
ukssdc_w = {}
}
@article{Willis2016a,
author = {Willis, D. M. and Wild, M. N. and Warburton, J. S.},
title = {Re-examination of the Daily Number of Sunspot Groups for the
Royal Observatory, Greenwich
(1874\thinspace--\thinspace1885)},
journal = {Solar Physics},
year = {2016},
pages = {1--34},
abstract = {The daily number of sunspot groups on the solar disk, as
recorded by the programme of sunspot observations performed
under the aegis of the Royal Observatory, Greenwich, UK, and
subsequently the Royal Greenwich Observatory (RGO), is
re-examined for the interval
1874\thinspace--\thinspace1885. The motivation for this
re-examination is the key role that the RGO number of
sunspot groups plays in the calculation of Group Sunspot
Numbers (Hoyt and Schatten in Solar Phys. 179, 189, 1998a;
Solar Phys. 181, 491, 1998b). A new dataset has been
derived for the RGO daily number of sunspot groups in the
interval 1874\thinspace--\thinspace1885. This new dataset
attempts to achieve complete consistency between the sunspot
data presented in the three main sections of the RGO
publications and also incorporates all known errata and
additions. It is argued that days for which no RGO solar
photograph was acquired originally should be regarded,
without exception, as being days without meaningful sunspot
data. The daily number of sunspot groups that Hoyt and
Schatten assign to days without RGO photographs is
frequently just a lower limit. Moreover, in the absence of a
solar photograph, the daily number of sunspot groups is
inevitably uncertain because of the known frequent
occurrence of sunspot groups that exist for just a single
day. The elimination of days without photographs changes the
list of inter-comparison days on which both the primary RGO
observer and a specified secondary comparison observer saw
at least one sunspot group. The resulting changes in the
personal correction factors of secondary observers then
change the personal correction factors of overlapping
tertiary observers, etc. In this way, numerical changes in
the personal correction factors of secondary observers
propagate away from the interval
1874\thinspace--\thinspace1885, thereby potentially changing
the arithmetical calculation of Group Sunspot Numbers over
an appreciably wider time interval.},
issn = {1573-093X},
doi = {10.1007/s11207-016-0856-7},
url = {http://dx.doi.org/10.1007/s11207-016-0856-7},
pdf = {http://link.springer.com/content/pdf/10.1007%2Fs11207-016-0856-7.pdf},
ukssdc_w = {}
}
@article{willis1996,
author = {Willis, D.M. and Davda, V.N. and Stephenson, F.Richard},
title = {Comparison between Oriental and Occidental Sunspot
Observations},
journal = {Quarterly Journal of the Royal Astronomical Society},
pages = {189--229},
year = {1996},
month = {jun},
volume = {37},
ukssdc_w = {}
}
@article{willis09:_presen_of_large_sunsp_near,
author = {Willis, D.M. and Henwood, R. and Stephenson, F.R.},
title = {The presence of large sunspots near the central solar
meridian at the times of major geomagnetic storms},
journal = {Annales Geophysicae},
year = 2009,
volume = 27,
pages = {185--197},
number = {1},
url = {http://www.ann-geophys.net/27/185/2009/},
month = jan,
abstract = {A further study is made of the validity of a technique
developed by the authors to identify historical occurrences
of intense geomagnetic storms, which is based on finding
approximately coincident observations of sunspots and
aurorae recorded in East Asian histories. Previously, the
validity of this technique was corroborated using scientific
observations of aurorae in Japan during the interval
1957--2004 and contemporaneous white-light images of the Sun
obtained by the Royal Greenwich Observatory, the Big Bear
Solar Observatory, the Debrecen Heliophysical Observatory,
and the Solar and Heliospheric Observatory spacecraft. The
present investigation utilises a list of major geomagnetic
storms in the interval 1868--2008, which is based on the
magnitude of the AA* magnetic index, and reconstructed solar
images based on the sunspot observations acquired by the
Royal Greenwich Observatory during the shorter interval
1874--1976. It is found that a sunspot large enough to be
seen with the unaided eye by an "experienced" observer was
located reasonably close to the central solar meridian for
almost 90\% of these major geomagnetic storms. Even an
"average" observer would easily achieve a corresponding
success rate of 70\% and this success rate increases to
about 80\% if a minority of ambiguous situations are
interpreted favourably. The use of information on major
geomagnetic storms, rather than modern auroral observations
from Japan, provides a less direct corroboration of the
technique for identifying historical occurrences of intense
geomagnetic storms, if only because major geomagnetic storms
do not necessarily produce auroral displays over East
Asia. Nevertheless, the present study provides further
corroboration of the validity of the original technique for
identifying intense geomagnetic storms. This additional
corroboration of the original technique is important because
early unaided-eye observations of sunspots and aurorae
provide the only possible means of identifying individual
geomagnetic storms during the greater part of the past two
millennia.},
ukssdc_w = {}
}
@article{willis07:_sporadic_aurorae,
user = {r.henwood@rl.ac.uk},
author = {Willis, D.M. and Stephenson, F. R. and Huiping Fang},
title = {Sporadic aurorae observed in East Asia},
journal = {Annales Geophysicae},
volume = {25},
number = {2},
pages = {417-436},
year = {2007},
month = mar,
url = {http://www.ann-geophys.net/25/417/2007/angeo-25-417-2007.html},
pdf = {http://www.ann-geophys.net/25/417/2007/angeo-25-417-2007.pdf},
ukssdc_w = {},
abstract = {All the accessible auroral observations recorded in Chinese
and Japanese histories during the interval AD 1840--1911 are
investigated in detail. Most of these auroral records have
never been translated into a Western language before. The
East Asian auroral reports provide information on the date
and approximate location of each auroral observation,
together with limited scientific information on the
characteristics of the auroral luminosity such as colour,
duration, extent, position in the sky and approximate time
of occurrence. The full translations of the original Chinese
and Japanese auroral records are presented in an appendix,
which contains bibliographic details of the various
historical sources. (There are no known reliable Korean
observations during this interval.) A second appendix
discusses a few implausible "auroral" records, which have
been rejected. The salient scientific properties of all
exactly dated and reliable East Asian auroral observations
in the interval AD 1840--1911 are summarised succinctly. By
comparing the relevant scientific information on exactly
dated auroral observations with the lists of great
geomagnetic storms compiled by the Royal Greenwich
Observatory, and also the tabulated values of the Ak
(Helsinki) and aa (Greenwich and Melbourne) magnetic
indices, it is found that 5 of the great geomagnetic storms
(aa>150 or Ak>50) during either the second half of the
nineteenth century or the first decade of the twentieth
century are clearly identified by extensive auroral displays
observed in China or Japan. Indeed, two of these great
storms produced auroral displays observed in both countries
on the same night. Conversely, at least 29 (69\%) of the 42
Chinese and Japanese auroral observations occurred at times
of weak-to-moderate geomagnetic activity (aa or
Ak$\leq$50). It is shown that these latter auroral displays
are very similar to the more numerous (about 50) examples of
sporadic aurorae observed in the United States during the
interval AD 1880--1940. The localised nature and spatial
structure of some sporadic aurorae observed in East Asia is
indicated by the use of descriptive terms such as
"lightning", "rainbow", "streak" and "grid".}
}
@article{willis79:_statis,
author = {Willis, D.M. and Tulunay, Y.K.},
title = {Statistics of the largest sunspot and facular areas per
solar cycle},
journal = {Solar Physics},
pages = {237--246},
year = {1979},
volume = {64},
abstract = {The paper uses the statistics of extreme values to
investigate the statistical properties of the largest areas
of sunspots and photospheric faculae per solar cycle. The
largest values of the synodic-solar-rotation mean areas of
umbrae, whole spots and faculae, which have been recorded
for nine solar cycles are shown to comply with the general
form of the extreme value probability function. Empirical
expressions are derived for the three extreme value
populations from which the characteristic statistic
parameters, namely the mode, median, mean and standard
deviation, can be calculated for each population. It is
found that extreme areas of umbrae and whole spots have a
diversion comparable to that found by Siscoe for the extreme
values of sunspot number whereas the extreme areas of
faculae have a smaller dispersion which is comparable to
that found by Siscoe for the largest geomagnetic storm per
solar cycle.},
ukssdc_w = {}
}
