Eskdalemuir Observatory Research Articles

Atmospheric electricity observations at Eskdalemuir Geophysical Observatory

Abstract. Atmospheric electricity measurements, principally of the hourly potential gradient (PG), were made continuously at Eskdalemuir Observatory, Scotland (55.314° N, 3.206° W), between 1911 and 1981. Air ion properties were also determined. The sensing apparatus for PG measurement at Eskdalemuir initially used a Kelvin water dropper potential equaliser (1911–1936), followed by a radioactive probe from 1936 and, from 1965, a horizontal stretched wire sensor at 0.5 m, all attached to recording devices. Monthly mean PG data from these instruments are now available digitally. Originally, the data were classified into undisturbed and disturbed days, using the chart record (electrogram). This approach has deficiencies at Eskdalemuir due to mist, fog and calm conditions, which can influence the mean PG despite the day appearing undisturbed on the electrogram. Nevertheless, a correlation with Pacific Ocean temperature fluctuations is apparent in the Eskdalemuir PG data between 1911 and 1950. As at Lerwick, there was an abrupt decrease in the PG caused by nuclear weapon detonations in the late 1950s and early 1960s. The 1950s PG decrease began at Eskdalemuir before that at Lerwick, for which possible additional local factors are evaluated.

Climatology of the Harmonic Frequency Separation of Ionospheric Alfvén Resonances at Eskdalemuir Observatory, UK

AbstractWe extracted the harmonic frequency separation (Δf) of Ionospheric Alfvén Resonances (IAR) observed in the Eskdalemuir induction coil magnetometer data for the 9 year data set of 2013–2021. To obtain Δf values, we used a machine learning technique that identifies the harmonics and from this we calculated the average separation. To investigate the climatology of the IAR, we have modeled the Δf of the IAR for the data set using a time of flight calculation with model Alfvén velocity profiles. When analyzing Δf from the model and data, we found that in general they follow the same trends. The modeled Δf and Δf from the data both show an inverse correlation with foF2, which confirms that the frequencies of the IAR are controlled by electron density. It follows that Δf is greater around midnight and during the winter months, due to the decrease in plasma mass density. Variability is also reflected when comparing yearly trends in Δf with the sunspot number; higher frequencies are observed and modeled at low sunspot number. It is difficult to examine trends with instantaneous geomagnetic activity as IAR are not visible in spectrograms when geomagnetic activity is high. We find cases where the difference in measured and modeled Δf is significant, suggesting that the model does not capture short term variations in plasma mass density that influence the IAR during these days. We plan to undertake further modeling of Δf on shorter timescales.

Seismographs at Eskdalemuir Observatory, 1908–1925: tools for rethinking the origins of international cooperation in seismology

The British seismologist John Milne (1850–1913) is a dominant and celebrated figure in historical accounts of seismology. In this paper I use evidence from seismographs preserved in the collections of the Science Museum Group to reconsider his contribution, particularly to the progress of international collaboration in seismology. These instruments were installed at Eskdalemuir Observatory in Dumfriesshire, Scotland between 1908 and 1925; not only were they situated far from Milne’s private observatory on the Isle of Wight, but they represented examples of Russian, Japanese and German seismograph design as well as Milne’s own. No other site in Britain boasted such an international suite of earthquake instruments. Together, they reveal an alternative vantage-point from which to view his influence. By attending closely to the instruments’ provenance, I show how the collection can be a powerful tool for decentring the hagiography that surrounds the so-called ‘Father of Modern Seismology’.

Automatic detection of Ionospheric Alfvén Resonances in magnetic spectrograms using U-net

Ionospheric Alfvén Resonances (IARs) are weak discrete non-stationary Alfvén waves along magnetic field lines, at periods of ∼0.5–20 Hz, that occur during local night-time, particularly during low geomagnetic activity. They are detectable through time–frequency analysis (spectrograms) of measurements made by sensitive search coil magnetometers. The IARs are generated by the interaction of electromagnetic energy partially trapped in the Earth–ionosphere cavity with the main geomagnetic field and their behaviour provides proxy information about atmospheric ion density between 100–1000 km altitude. Limited methods exist to automatically detect and analyse their properties and behaviour as they are difficult to extract using standard image and signal processing techniques. We present a new method for the detection of IARs based on the fully convolutional neural network U-net. U-net was chosen as it is able to perform accurate image segmentation and it can be trained in a supervised fashion on a relatively small labelled dataset utilizing data augmentation. We show that the resulting predictive model generated by training the U-net is able to detect IAR signals while mislabelling considerably less noise than other data analysis methods. We achieved our best results by using a training set of 178 hand-digitized examples from high-quality spectrograms measured at the Eskdalemuir Geophysical Observatory (UK). We find that the network converges in ten iterations with a final intersection over union (IoU) metric of 0.9 and a training loss of below 0.2. We use the trained network to extract IARs from over 2300 images, covering six years of search coil magnetometer data measured at the Eskdalemuir Observatory. U-net can also automatically handle missing data or days without IARs, giving a null result as expected. This constitutes the first use of a neural network for pattern recognition of unstructured image data such as spectrograms containing IAR signals, though the method is applicable to other types of resonances or geophysical features in the time–frequency domain.

Is the Madden–Julian Oscillation reliably detectable in Schumann Resonances?

The Madden–Julian Oscillation (MJO) is a quasi-periodic (∼30–90 days) eastward-moving atmospheric mode which primarily modifies rainfall patterns in the equatorial regions from Africa to the Pacific Ocean. It has been proposed that its signature is detectable within the intensity variations of the Schumann Resonances (SR) due to changes in the location and magnitude of the major lightning centres. Using six years of induction coil data recorded at the Eskdalemuir Observatory in the UK, we investigate whether the MJO is detectable in the first three Schumann Resonances. We extract the frequency and intensity values from each resonance every 10 min, averaged to a daily value and compare them to the Realtime Multivariate MJO (RMM) index. We use Empirical Mode Decomposition (EMD) to determine if certain modes correlate between the SR and RMM curves. We find that the EMD 30–70 day modes of the SR and RMM index occasionally beat in-phase during the La Niña periods of the El Niño Southern Oscillation (ENSO) but not El Niño periods. However, the relationship is not wholly consistent, implying that robust and reliable detection of the MJO in SR data remains challenging.

Observation of Ionospheric Alfvén Resonances at 1–30 Hz and Their Superposition With the Schumann Resonances

AbstractLong‐term measurements of the high‐frequency magnetic field (0.1–100 Hz) have been made at Eskdalemuir Observatory in the United Kingdom since September 2012. We analyze five years of dynamic spectrograms to examine the occurrence and behavior of the Schumann and ionospheric Alfvén resonances (IAR) and Pc1 pulsations. The resonances, observed as diffuse bands, arise from reflections of energy both within the Earth‐ionosphere cavity and from the nonlinear conductivity gradient of the ionosphere. Schumann Resonances (SR) occur continuously but IAR are observed to arise at local nighttime in ∼50% of days in the data set. Typically, IAR are found at frequencies of 1–8 Hz, but we find them extending out to 30 Hz and strongly superimposing over the first three Schumann resonances around 9% of the time. These phenomena include constructive and destructive interference, nonlinear frequency changes over the span of several hours, and polarity enhancements. In addition, the magnitude of the IAR does not decline rapidly with frequency as often proposed. We find that the IAR and their superposition with SR are strongly controlled by season and geomagnetic activity. We compare 6 days with the most unusual IAR behavior in the data set to ionosonde measurements of f0F2, a proxy for ionospheric conductivity but find little correlation. We suggest that, as current theoretical modeling does not account for these observations, further work is needed to understand how they arise.

Resolving issues concerning Eskdalemuir geomagnetic hourly values

Abstract. The hourly values of the geomagnetic field from 1911 to 1931 derived from measurements made at Eskdalemuir observatory in the UK, and available online from the World Data Centre for Geomagnetism at http://www.wdc.bgs.ac.uk/, have now been corrected. Previously they were 2-point averaged and transformed from the original north, east and vertical down values in the tables in the observatory yearbooks. This paper documents the course of events from discovering the post-processing done to the data to the final resolution of the problem. As it was through the development of a new index, the Inter-Hour Variability index, that this post-processing came to light, we provide a revised series of this index for Eskdalemuir and compare it with that from another European observatory. Conclusions of studies concerning long-term magnetic field variability and inferred solar variability, whilst not necessarily consistent with one another, are not obviously invalidated by the incorrect hourly values from Eskdalemuir. This series of events illustrates the challenges that lie ahead in removing any remaining errors and inconsistencies in the data holdings of different World Data Centres.

Correcting the geomagnetic IHV index of the Eskdalemuir observatory

Abstract. We study here the recently proposed measure of local geomagnetic activity called the IHV (Inter-Hour Variability) index calculated for the Eskdalemuir (ESK) station. It was found earlier that the ESK IHV index depicts an artificial, step-like increase from 1931 to 1932. We show here that this increase is due to the fact that the values of the magnetic field components of the ESK observatory stored at the World Data Center are two-hour running averages of hourly data stored in ESK yearbooks. Two-hour averaging greatly reduces the variability of the data which leads to artificially small values of the IHV index in 1911–1931. We also study the effect of two-hour averaging upon hourly mean and spot values using 1-minute data available for recent years, and calculate the correction factors for the early years, taking into account the weak dependence of correction factors on solar activity. Using these correction factors, we correct the ESK IHV indices in 1912–1931, and revise the estimate of the centennial change based on them. The effect of correction is very significant: the centennial increase in the ESK IHV-raw (IHV-cor) index in 1912–2000 changes from 73.9% (134.4%) before correction to 10.3% (25.3%) thereafter, making the centennial increase at ESK quite similar to other mid-latitude stations. Obviously, earlier long-term studies based on ESK IHV values are affected by the correction and need to be revised. These results also strongly suggest that the ESK yearbook data should be digitized and the hourly ESK data at WDC should be replaced by them.

Eskdalemuir Observatory

WeatherVolume 60, Issue 3 p. 66-69 Research Article Eskdalemuir Observatory I. K. Dawson, Corresponding Author I. K. Dawson ian.dawson@metoffice.gov.uk Met Office Real-Time Monitoring Centre, Eskdalemuir ObservatoryMet Office, Eskdalemuir Observatory, Langholm, Dumfries shire DG13 0QW.Search for more papers by this author I. K. Dawson, Corresponding Author I. K. Dawson ian.dawson@metoffice.gov.uk Met Office Real-Time Monitoring Centre, Eskdalemuir ObservatoryMet Office, Eskdalemuir Observatory, Langholm, Dumfries shire DG13 0QW.Search for more papers by this author First published: 29 December 2006 https://doi.org/10.1256/wea.218.03Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume60, Issue3March 2005Pages 66-69 RelatedInformation

Long-term changes in atmospheric electrical parameters observed at Nagycenk (Hungary) and the UK observatories at Eskdalemuir and Kew

Abstract. The Nagycenk Geophysical Observatory in Hungary (47° 38 ' N, 16° 43 ' E) has made continuous measurements of the vertical atmospheric electric Potential Gradient (PG) since 1962. Global signals have previously been identified in the Nagycenk PG data. A long-term (1920–1981) decrease has been discovered in the PG measured at the Eskdalemuir Observatory, Scotland (55° 19 ' N, 3° 12 ' W), suggesting that this represents a global change in the atmospheric electricity related to a decline in cosmic rays. A 40% decline in PG is shown here to have occurred at Nagycenk between 1962 and 2001, also consistent with changes in the air-Earth current measured at Kew (51° 28 ' N, 0° 19 ' W), London, 1966–1978. Comparison of the long-term PG measurements at both Eskdalemuir and Nagycenk gives further evidence to support the hypothesis of a global atmospheric electrical decline from the early twentieth century to the present time, as it is shown that local effects at Nagycenk are unlikely to have dominated the changes there.Key words. Meteorology and atmospheric dynamics (atmospheric electricity)

Nonlinear and multifractal approaches of the geomagnetic field

Recent nonlinear dynamics techniques have been developed to analyse chaotic time series data. We first summarize the procedure which gives an appropriate reconstruction of the unknown dynamics from scalar measurements in a pseudophase space. It permits, firstly, the representation of the trajectories of the dynamical system—they define an attractor when the system is dissipative—by preserving its topological properties. We then present the invariant measures and ergodic quantities such as the multifractal spectrum and Lyapunov exponents which can be estimated on the reconstructed attractor. The multifractal analysis provides us with a characterization of the scaling energy of the process whereas the Lyapunov exponent gives another statistical measure of the stability of the dynamics. The estimation of these quantities was tested on synthetic data. The nonlinear and multifractal analyses were finally applied to the hourly mean values of the magnetic field recorded at the Eskdalemuir (ESK) observatory over 79 years (692,520 data measurements for each component). The estimations of a 5-dimensional pseudo-phase space and a positive Lyapunov exponent confirm the possibility of low-dimensional deterministic chaos in the magnetic field observations at ESK observatory. The correlation between the solar activity (the Wolf number), the unstable nature of the magnetic field, and the singularity spectrum points out the forcing of the solar cycles on the dynamics of the magnetic field at ESK observatory.

“Weather-type” Frequencies and Temperature Fluctuation: a Reply

LAWRENCE'S information on possible factors affecting the temperature record at Eskdalemuir Observatory, which we had unfortunately overlooked, is appreciated. It is, however, difficult to find suitable neighbouring stations, with homogeneous data series in a conveniently available form. With respect to the possible shelterbelt effects, the tendency would be towards higher maxima and lower minima in 1957–67 than in 1925–35. In fact, for anticyclonic type, which should best reflect this influence, the maxima and minima increase or decrease together in all four months investigated.

Magneto-Telluric Investigations in the Irish Sea and Southern Scotland

Summary The magneto-telluric field, in the spectrum 8 s to 100 min, has been recorded at four stations, Eskdalemuir (lat 55°17′ N, long 3°11′W), Portpatrick (54°51′ N, 5°5′W), Port Erin (54°5′N, 4°45′W) and Nefyn (52°56′ N, 4°33′ W). Records of E were obtained simultaneously on two short cables orientated N-S and E-W at Eskdalemuir, the H variations being obtained from the observatory records there. At the other stations E was recorded on six cables (9-120 km long), five of which cross part or all of the Irish Sea. The measurements were made on each cable in turn. At each station the component of H orthogonal to the cable was also measured. Assuming a top layer of resistivity 3000 ohm-metres, the profiles at Eskdalemuir indicate a thickness for this layer of 12 km. Underlying this is a layer of resistivity 45 ohm-metres which extends to a depth of 30 km; beneath this the resistivity is about 2500 ohm-metres. These results do not depend critically upon the resistivity assumed for the top layer. After corrections have been made for the estimated thickness and resistivity of the sediments in the Irish Sea, the results from five of the six long cables confirm the presence of a low resistivity (10-100 ohm-metres) layer in the middle or lower part of the crust. On comparison of the magnetic field records with the magnetograms of Eskdalemuir observatory, it was found that, although the shape of the pulsations was similar at all stations, the amplitude ratios between stations showed considerable dependence upon the period of the oscillations. This can be explained largely by anomalies in conductivity near Nefyn and Port Erin. It appears unlikely that sedimentary basins in the Irish Sea can account for more than a small part of the anomalies. The effect of finite dimensions of the source is discussed; corrections for a possible variation of the field dimension have been made and it is found that these do not materially affect the results. Possible induction effects of the Atlantic Ocean have been considered and it is concluded that these have been negligible in this survey.

XXVI.—On the Vertical Force Changes during the “Sudden Commencement” of a Magnetic Storm

About six years ago I communicated to the Society an account of some measurements made at Eskdalemuir Observatory of the more minute changes which are almost continually occurring in the vertical component of the earth's magnetic field. The method adopted was that of connecting the terminals of a coil of wire, whose axis is vertical, to a suitable galvanometer on which was measured the current induced in the coil by changes in the vertical component of the terrestrial field.

British Meteorological and Magnetic Year Book, 1920

THIS publication comprises the daily values of the meteorological and geophysical elements at three observatories of the Meteorological Office, namely, Kew Observatory, Richmond; Valencia Observatory in Ireland; and Eskdalemuir Observatory, Dumfriesshire; and at the St. Louis Observatory in Jersey: daily values of solar radiation at South Kensington; wind components at fixed hours at four anemograph stations; tabulations of occasional soundings of the upper air; and results of observations of cloud and aurora. The annual supplement contains upper air temperatures by means of soundings with registering balloons and aeroplane ascents, giving monthly and annual averages with averages for the period 1917–1920; notes on seismological work at Eskdalemuir Observatory; the water-level recorder at Kew Observatory; and tables of monthly means of magnetic and electrical data for Eskdalemuir and Richmond respectively.

The Magnetic Storm of August 11–12, 1919

THE magnetic storm which began on the morning of August 11 was one of the largest recorded in recent years, and was probably of world-wide distribution. It attracted public attention chiefly through the notable—though not unusual—extent to which it interfered with telegraphic work. On account of its somewhat exceptional features, the following statement of results of observations at Eskdalemuir Observatory may be of some interest, and is communicated by permission of the Director, Meteorological Office.

The magnetic storm of December 16-17, 1917, as recorded at Kew and Eskdalemuir observatories

1. In a recent paper, I described a magnetic storm occurring on August 22, 1916, in which the disturbances recorded at Kew and Eskdalemuir Observatories were closely similar in type. The magnetic storm on December 16-17, 1917, affords in many ways a remarkable contrast, the changes recorded at the two observatories differing notably in type. The disturbance was the largest of the year. In the Kew declination (D) and horizontal force (H) curves, a prominent feature was a succession of oscillations with periods of about 20 minutes, and it was the hope of identifying these with corresponding oscillations at Eskdalemuir that suggested the present investigation. Dr. Crichton Mitchell, the Superintendent of Eskdalemuir Observatory, kindly sent the original curves, so the comparison was made under favourable conditions. One of the obstacles to the identification of corresponding movements at the two stations is that, while H and D are recorded at Kew, the north (N) and west (W) components are recorded at Eskdalemuir. On instituting a minute comparison between the Kew H and D curves, it was found that, while oscillations with periods not far from 20 minutes were prominent in both, the times of the turning points by no means always agreed. A turning point in the H curve, for instance, might be represented by a short arrest or slight temporary reversal of movement in the D curve, the original direction of the D movement being almost immediately resumed. Again, towards the end of an oscillation, the trace might be nearly level for some minutes, or there might be a small short period oscillation, so that more than one choice was possible when assigning a time for the end of one major oscillation or the beginning of the next. Thus, when one had to compare Kew H with Eskdalemuir N curves, and Kew D with Eskdalemuir W curves, the fact that corresponding movements were difficult to identify is not surprising. Both observatories record vertical force (V), but the Kew V curves are so much disturbed by artificial electrical currents that they cannot be relied on for minor details. There were also difficulties special to the particular storm. Some of the N and W movements at Eskdalemuir were so rapid that the photographic trace was in places almost invisible. While the time marks occur on the base lines as well as on the curve lines, there is sensible parallax, and when the marks on the curve lines become invisible, the time cannot be fixed with quite the usual accuracy.

Seismic Disturbances Connected with the Guatemala Earthquake

IN view of the widespread destruction caused by the earthquake in Guatemala, the accompanying notes, written by Dr. Crichton Mitchell, superintendent of Eskdalemuir Observatory, are of interest. We are in debted to the Director of the Meteorological Office for these notes, and are glad to be able to publish them.

University and Educational Intelligence.

SHEFFIELD.—The council of the University of Sheffield has made the following appointments:—(i) Dr. H. R. Dean, to the Joseph Hunter chair of pathology, in succession to Prof. J. M. Beattie, who has been appointed to the chair of bacteriology in the University of Liverpool. Dr. Dean is at present assistant bacteriologist to the Lister Institute of Preventive Medicine. (2) Mr. Leonard Southerns, to the post of junior lecturer and demojistratpr in physics, vice Dr. J. Robinson, resigned. Mr. Southerns is at present chief assistant at the Eskdalemuir Observatory, N.B. The council received the resignation of Prof. F. W. Hardwick of the professorship of mining, owing to his retirement from active work. Prof, Hardwick has been on the staff since October, 1891.

The Recent Earthquakes in Asia

I AM informed by Mr. G. W. Walker, superintendent of Eskdalemuir Observatory, that the records of the seismograph according to the design of Prince Boris Galitzine, which was recently presented by Dr. Arthur Schuster to the observatory, give the positions of the epicentres of the recent earthquakes in Asia as follows:— January 1, lat. 36½° N., long. 66° E. January 3–4, lat. 42° N., long. 77° E.