I am a professor of acoustic imaging and signal processing at the University of Oslo and an elected member of the Norwegian Academy of Technological Sciences. Jointly with the Digital Signal Processing and Image Analysis group we were part of "Centre for Innovative Ultrasound Solutions (CIUS)" - a centre for research-based innovation from 2015-24.
My main interest is to understand the physics of wave propagation in complex media like biological tissue. Cosmologist and astrophysicist Martin Rees says:
We can expect huge advances on three frontiers: the very small, the very large, and the very complex
More specifically I want to understand why wave propagation in complex media in medical ultrasound and elastography often results in power law frequency characteristics (attenuation and dispersion), and to uncover the physical basis for non-integer (fractional) derivative descriptions of waves - if indeed there is one.
From time to time I am on the panel of the popular national radio show NRK P2, "Tower of Abel" answering questions on acoustics in a wide sense and sometimes commenting on the history/philosophy of science. I have blogged since 2010, mainly in Norwegian, and some in English.
Apart from that I probably have too many interests. That includes history and philosophy of science, loudspeakers/audio coding, and amateur radio.
Books
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"Waves with Power-Law Attenuation," 2019, Springer and ASA Press. Corrected version in 2023.
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The imagined conflict: On science and God, Oct. 2021, written in Norwegian: Den innbilte konflikten. Om naturvitenskap og Gud. (Titel auf deutsch: Der eingebildete Konflikt. Über Naturwissenschaft und Gott.)
History/philosophy of science
Research
Acoustics and Waves
Fractional Derivatives
Other Presentations
Software
The publication list from the database Cristin is not always so useful as it seems to be unable to distinguish between publications from several persons with the same name as me. Therefore it may be better to use my own list, Google Scholar, or ORCID.
Tags:
Acoustics,
medical imaging,
ultrasound,
non-integer (fractional) derivatives,
signal processing,
elastography
Publications
Most cited papers
- J.-F. Synnevåg, A. Austeng, and S. Holm, "Adaptive beamforming applied to medical ultrasound imaging," IEEE Trans. Ultrason., Ferroelect., Freq. Contr. (Special issue on high resolution ultrasonic imaging), vol. 54(8), Aug. 2007, pp. 1606-1613.
- W. Chen and S. Holm, "Fractional Laplacian time-space models for linear and nonlinear lossy media exhibiting arbitrary frequency dependency," J. Acoust. Soc. Amer., pp. 1424-1430, Apr. 2004.
- J.-F. Synnevåg, A. Austeng, and S. Holm, ”Benefits of Minimum-Variance Beamforming in Medical Ultrasound Imaging”, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., Sept. 2009.
- A. Austeng and S. Holm, "Sparse 2D Arrays for 3D Phased Array Imaging - Design Methods," IEEE Trans. Ultrasonics, Ferroelectrics and Frequency Control, Aug. 2002, pp. 1073-1086.
- W. Chen and S. Holm, "Modified Szabo’s wave equation models for lossy media obeying frequency power law," J. Acoust. Soc. Amer., pp. 2570-2574, Nov. 2003.
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Chotiros, Nicholas P. & Holm, Sverre
(2024).
Modeling and simulation of underwater acoustic propagation through a random distribution of ice blocks.
JASA Express Letters.
ISSN 2691-1191.
4(3).
doi:
10.1121/10.0025395.
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Frissell, Nathaniel A.; Ackerman, John R.; Alexander, Jesse N.; Benedict, Robert L.; Blackwell Jr., William C. & Boedicker, Rachel K.
[Show all 64 contributors for this article]
(2023).
Heliophysics and amateur radio: citizen science collaborations for atmospheric, ionospheric, and space physics research and operations.
Frontiers in Astronomy and Space Sciences.
10.
doi:
10.3389/fspas.2023.1184171.
Full text in Research Archive
Show summary
The amateur radio community is a global, highly engaged, and technical community with an intense interest in space weather, its underlying physics, and how it impacts radio communications. The large-scale observational capabilities
of distributed instrumentation fielded by amateur radio operators and radio science enthusiasts offers a tremendous opportunity to advance the fields of heliophysics, radio science, and space weather. Well-established amateur radio networks like the RBN, WSPRNet, and PSKReporter already provide rich, ever-growing, long-term data of bottomside ionospheric observations. Up-and-coming purpose-built citizen science networks, and their associated novel
instruments, offer opportunities for citizen scientists, professional researchers, and industry to field networks for specific science questions and operational needs. Here, we discuss the scientific and technical capabilities of the global amateur radio community, review methods of collaboration between the
amateur radio and professional scientific community, and review recent peerreviewed studies that have made use of amateur radio data and methds. Finally, we present recommendations submitted to the U.S. National Academy of
Science Decadal Survey for Solar and Space Physics (Heliophysics) 2024–2033 for using amateur radio to further advance heliophysics and for fostering deeper collaborations between the professional science and amateur radio
communities. Technical recommendations include increasing support for distributed instrumentation fielded by amateur radio operators and citizen scientists, developing novel transmissions of RF signals that can be used in citizen science experiments, developing new amateur radio modes that
simultaneously allow for communications and ionospheric sounding, and formally incorporating the amateur radio community and its observational assets into the Space Weather R2O2R framework. Collaborative recommendations include allocating resources for amateur radio citizen science research projects and activities, developing amateur radio research and educational activities in collaboration with leading organizations within the amateur radio community,
facilitating communication and collegiality between professional researchers and amateurs, ensuring that proposed projects are of a mutual benefit to both the professional research and amateur radio communities, and working towards
diverse, equitable, and inclusive communities.
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Chandrasekaran, Sri Nivas; Holm, Sverre & Näsholm, Sven Peter
(2023).
Wave equations of the two common sediment acoustic theories.
Proceedings of Meetings on Acoustics (POMA).
ISSN 1939-800X.
51.
doi:
10.1121/2.0001795.
Full text in Research Archive
Show summary
Two popular theories for wave propagation in sediments, the Biot poroelastic theory and the Viscous Grain Shearing (VGS) theory, have been formulated in terms of dispersion relations. The lack of explicit wave equations for these models could be considered to be a weakness. Hence, providing wave equations that are fully consistent with these theories might confirm that they have a physical basis. In the Biot theory, it is the frequency-dependent viscodynamic operator that poses the problem as there is no equivalent time-domain operator. Previous work has shown that this factor can be approximated well with a simplified square root operator. Drawing on the parallel to the Cole-Davidson dielectric theory for complex media where the same factor appears, and using the equivalent time-domain operator, which is a fractional pseudo-differential operator, enables the formulation of wave equations for all three wave modes of the Biot theory. The same operator turns out to be central for transforming the dispersion relations of the VGS theory to time-space wave equations. In this case, the relation between the dispersion equations and the wave equations is exact. The wave equations of these two theories will enable a closer study of the properties of the medium models.
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Marthinsen, Eirik Brenner & Holm, Sverre
(2023).
Difference between Charge–Voltage Relations of Ordinary and Fractional Capacitors.
Fractal and Fractional.
7(11).
doi:
10.3390/fractalfract7110781.
Full text in Research Archive
Show summary
In an ordinary time-varying capacitor, there is debate on whether a time-domain multiplication or a time-domain convolution of capacitance and voltage determines charge. The objective of this work is to resolve this question by experiments on a time-varying capacitor in parallel with a resistor. It was implemented by a motor-driven potentiometer and op-amps. The response matched a power-law function over about two decades of time, and not an exponential, for several sets of parameters. This confirms the time-domain multiplication model. This result is the opposite of that obtained for a constant phase element (CPE) in its common time- and frequency-varying capacitor interpretation. This demonstrates that a CPE is fundamentally different from an ordinary time- and frequency-varying capacitor.
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Holm, Sverre; Chandrasekaran, Sri Nivas & Näsholm, Sven Peter
(2023).
Adding a low frequency limit to fractional wave propagation models.
Frontiers in Physics.
ISSN 2296-424X.
11,
p. 1–8.
doi:
10.3389/fphy.2023.1250742.
Full text in Research Archive
Show summary
Power-law attenuation in elastic wave propagation of both compressional and shear waves can be described with multiple relaxation processes. It may be less physical to describe it with fractional calculus medium models, but this approach is useful for simulation and for parameterization where the underlying relaxation structure is very complex. It is easy to enforce a low-frequency limit on a relaxation distribution and this gives frequency squared characteristics for low frequencies which seems to fit some media in practice. Here the goal is to change the low-frequency behavior of fractional models also. This is done by tempering the relaxation moduli of the fractional Kelvin-Voigt and diffusion models with an exponential function and the effect is that the low-frequency attenuation will increase with frequency squared and the square root of frequency respectively. The time-space wave equations for the tempered models have also been found, and for this purpose the concept of the fractional pseudo-differential operator borrowed from the field of Cole-Davidson dielectrics is useful. The tempering does not remove the singularity in the relaxation moduli of the models, but this has only a minor effect on the solutions.
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Aparicio Sosa, Joaquin; Alvarez, Fernando J.; Hernandez, Alvaro & Holm, Sverre
(2022).
A Survey on Acoustic Positioning Systems for Location-Based Services.
IEEE Transactions on Instrumentation and Measurement.
ISSN 0018-9456.
doi:
10.1109/TIM.2022.3210943.
Show summary
Positioning systems have become increasingly popular in the last decade for location-based services, such as navigation, and asset tracking and management. As opposed to outdoor positioning, where the global navigation satellite system became the standard technology, there is no consensus yet for indoor environments despite the availability of different technologies, such as radio frequency, magnetic field, visual light communications, or acoustics. Within these options, acoustics emerged as a promising alternative to obtain high-accuracy low-cost systems. Nevertheless, acoustic signals have to face very demanding propagation conditions, particularly in terms of multipath and Doppler effect. Therefore, even if many acoustic positioning systems have been proposed in the last decades, it remains an active and challenging topic. This article surveys the developed prototypes and commercial systems that have been presented since they first appeared around the 1980s to 2022. We classify these systems into different groups depending on the observable that they use to calculate the user position, such as the time-of-flight, the received signal strength, or the acoustic spectrum. Furthermore, we summarize the main properties of these systems in terms of accuracy, coverage area, and update rate, among others. Finally, we evaluate the limitations of these groups based on the link budget approach, which gives an overview of the system’s coverage from parameters such as source and noise level, detection threshold, attenuation, and processing gain.
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Chandrasekaran, Sri Nivas; Näsholm, Sven Peter & Holm, Sverre
(2022).
Wave equations for porous media described by the Biot model.
Journal of the Acoustical Society of America.
ISSN 0001-4966.
151(4),
p. 2576–2586.
doi:
10.1121/10.0010164.
Full text in Research Archive
Show summary
Single-mode equivalent space-time representations of the acoustic wave propagating in a Biot poroelastic medium have previously been found only for asymptotic cases: In the low frequency regime, where the viscous skin depth is greater than the characteristic pore size, the time domain equivalent is represented with integer order temporal and spatial loss terms, whereas in the high frequency regime, it is represented with fractional order temporal and spatial loss terms. In the current work, a time domain representation in terms of a partial differential equation is proposed for all three wave solutions of the Biot model across all frequencies, and it is derived from the material response function of the Biot poroelastic medium with suitable approximations for the compressional modes and the dynamic permeability. The dynamic permeability in the time domain is represented by a fractional pseudo-differential operator. Optimal correction factors are introduced into the wave equation to compensate for the discrepancies in the compressional wave dispersion and attenuation. Additionally, the method for incorporating the squirt flow mechanism into the wave equation via the Extended Biot poroviscoelastic model is described. The proposed wave equation has a physical basis and satisfies the passivity criterion.
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Aparicio, Joaquin & Holm, Sverre
(2021).
Obtaining range measurements from ambient noise cross-correlations for the self-calibration of nodes.
CEUR Workshop Proceedings.
ISSN 1613-0073.
3097.
Full text in Research Archive
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View all works in Cristin
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Holm, Sverre
(2024).
Den innbilte konflikten.
[Internet].
TVL.
Show summary
34:48 - En klok mann har sagt at når du tar en slurk av vitenskapens glass så blir du ateist. Men nederst i glasset så venter Gud på deg. Vår neste gjest er godt bevandret i natur-vitenskapelige kretser. Du har kanskje hørt stemmen hans tidligere. Han har nemlig vært jevnlig ekspert i radioprogrammet Abels Tårn og er fysiker ved Universitetet i Oslo. Fysikkprofessor Sverre Holm, hjertelig velkommen hit!
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Holm, Sverre
(2024).
10 kristne naturforskere du tenker på hver dag.
Show summary
Ampère, Volta, Kelvin, Lemaître, Anning, Faraday, Marconi, Newton, Townes, Steno
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Holm, Sverre
(2024).
John Lennox: The quest for artificial general intelligence and the limits of science.
[Internet].
YouTube.
Show summary
We humans are insatiably curious, and have always been asking questions, such as the hard questions about origin and destiny. With the rise of artificial intelligence, these questions have become even more daunting.
On the one hand, we live in a time of rapid scientific progress that holds enormous promise for many of the problems we face as humankind. So much so, in fact, that many see no need or use for other ways of solving the mysteries of our universe. They assume that science can explain everything.
On the other hand, popular answers to questions about artificial general intelligence differ wildly: from utopian vistas of superhumans working alongside superintelligent Al to Orwellian outcomes where humans are controlled or outcompeted by superintelligent machines or superior versions of themselves.
Lennox argues that the ethical considerations that we bring to bear on these questions is worldview dependent and has serious implications for our thinking about the future of humanity.
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Holm, Sverre
(2023).
Flukten fra lydene.
[Newspaper].
Aftenposten Innsikt.
Show summary
Du tror det er stille, men det er det egentlig aldri. Hva er lyd, og kan vi unnslippe den?
Skrevet av Anlov Peter Mathisen
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Holm, Sverre; Chandrasekaran, Sri Nivas & Näsholm, Sven Peter
(2023).
Finding wave equations for sediment acoustics theories.
Show summary
The two main theories for wave propagation in sediments, the Extended Biot theory and the Viscous Grain Shearing (VGS) theory, have been formulated in terms of dispersion equations only. Some have considered the lack of a wave equation to be a weakness that may indicate lack of a physical basis for these theories. In the Biot theory, it is the frequency-dependent viscodynamic operator which models viscous boundary effects in pores that poses the problem. It can be formulated as a ratio of Bessel functions for circular pores and as a ratio of tanh-functions for a 2D parallel plane duct. There is no simple equivalent time domain operator for use in the wave equation. In both geometries, the factor may, however, be approximated well with (1 + icω)1/2, where c is a constant. This factor also appears in the Cole-Davidson dielectric theory for complex media. The equivalent time domain operator, the fractional pseudo-differential operator, enables the formulation of wave equations for all three wave modes. The same operator turns out to be central for transforming the dispersion relations of the VGS theory to time-space wave equations. These wave equations enable a closer study of properties of the medium models than that obtained from dispersion relations alone.
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Holm, Sverre
(2023).
Natural Occurrence of Fractional Derivatives in Physics.
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Holm, Sverre
(2023).
Fractional derivatives appear wherever there are power laws in physics.
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Holm, Sverre
(2023).
The cautious acceptance of biological evolution by C S Lewis.
Show summary
“In the science, Evolution is a theory about changes: in the Myth, it is a fact about improvements” is what Lewis wrote in the Funeral of a Great Myth in the 1940’s, demonstrating both an acceptance of and a skepticism to the explanatory power of biological evolution.
There seems to be an ambiguity in reading Lewis, as Peterson in 2010 called him a theistic evolutionist, or an evolutionary theist, while West in 2012 said that Lewis does not fit in with mainstream theistic evolution.
First, this interest in Lewis’ views more than half a century after his death is remarkable. Second, the ambiguity more than anything else demonstrates the lack of precision in the label “theistic evolution” as Lewis cannot possibly both be supportive of it and against it at the same time.
Third, one cannot understand Lewis’ skepticism to explanations for improvements in evolution without considering his reading of Haldane, one of the founders of Neo-Darwinism. Nearly a century later, biologists still state that why the major evolutionary transitions happened defy explanation (Szathmáry, Smith, Nature 1995; Desmond, Biology & Philosophy, 2021). These transitions are different from the imprecise term macroevolution (up to the Phylum level), as they occur at an even higher level, e.g., from primates to human societies with natural language. Biologists seem to deal with this lack of explanation by either 1) accepting it, 2) by a more or less justified trust in a future resolution, or 3) by denying that there is progress at all, often leading to a low view of humans.
I argue here that Lewis’ views can still guide us today in expressing awe and wonder over the process of evolution as well as skepticism to the claims of evolutionism or the Myth, as Lewis liked to call it, that everything is explained.
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Holm, Sverre & Grøn, Øyvind
(2022).
Bokkronikk: Innføring i fysikk, Renstrøm og Renstrøm 2020.
Fra Fysikkens Verden.
ISSN 0015-9247.
84(3),
p. 60–63.
Show summary
Dette er en fysikkbok som ikke bare gjentar historiske myter, men går til orginalkildene for å gjengi historikken på en mest mulig korrekt måte. Anmelderne er meget positive til boken og håper at den vil bli brukt til å erstatte de ofte mytebefengte fremstillingene i enkelte andre norske lærebøker. Teksten er hele veien krydret med gode eksempler som er regnet gjennom på en passe detaljert måte slik at den uerfarne leser kan følge med hele veien. Boken er skrevet i et prima språk med god logikk i setningene.
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Davidsen, Bjørn Are & Holm, Sverre
(2022).
Når skal skolen avsløre myter i læremidler?
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Aftenposten (morgenutg. : trykt utg.).
ISSN 0804-3116.
Show summary
I 2020 trakk Gyldendal første utgave av «Falske Fakta» fra markedet. Grunnen var enkel: En bok om falske fakta presenterte selv falske fakta. Man fikk ikke straff i middelalderen «hvis man sa at Jorden var rund».
Kirken mente ikke «det var imot Bibelen» å mene dette.
Mytene finnes også i læremidler. En årsak kan være lærerutdanningen. Selv Svein Sjøbergs «Naturfag som allmenndannelse - en kritisk fagdidaktikk» lener seg mot myten om en lang konflikt mellom tro og vitenskap.
Likevel er nok populærvitenskap viktigere.
En så respektert formidler som Eirik Newth hevder i «Jakten på sannheten» at i middelalderen begynte mange kristne «å tro at Jorden var flat».
I stedet for å bli trukket fra markedet, er boken oversatt til 22 språk og fikk Brageprisen og Kulturdepartementets pris.
Slik fagsjekk.no viser, sprer Newth myte etter myte. Teologer lurte ikke på om kvinner hadde sjel. Sykehusene ble ikke stengt »fordi prestene fortalte at folk bare kunne bli friske ved å be til gud».
Kirken forbød ikke disseksjoner. Copernicus ventet ikke med å gi ut sin bok i frykt for kirkens reaksjoner. For bare å nevne noen.
Newth hevder at gudstro hemmer forskning, men nevner ikke at de fleste oppdagerne i boken har en gudstro.
Ja, en tro på mange guder styrker nok ikke jakten på lover i naturen, men tanken om Gud som lovgiver bak naturen kan ha bidratt avgjørende. Uansett nedtones oppdagernes tro. Selv en så engasjert kristen som Blaise Pascal blir den franske filosofen. Kardinal Nikolaus av Cusa som mente at verdensrommet er uendelig, kalles akademikeren.
Biskop Steno som argumenterte for at fossiler er forsteinede dyr og planter, er dansken.
Skal skolen leve opp til fagfornyelsen, bør mytene løftes frem som eksempler på hvor vanskelig kritisk tenkning er.
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Holm, Sverre
(2022).
Gud og vitenskap – Kan jeg tro på begge deler?
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Holm, Sverre
(2022).
En innbilt konflikt mellom naturvitenskap og gudstro?
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Holm, Sverre
(2022).
Gode grunner til at konflikten mellom vitenskap og Gud er innbilt.
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Aparicio, Joaquin; Thio, Vincent Martello Kwie Hoe & Holm, Sverre
(2022).
Range evaluation between indoor microphones obtained from acoustic ambient noise cross-correlations.
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Kvellestad, Anders; Normann, Ben David & Holm, Sverre
(2021).
Om Gud, fysikk og de dype spørsmålene.
Avisa Vårt land.
Show summary
EKSISTENS: Vi er både er fysikere og troende – og vi har like lite tro på julenissen, spøkelser eller «en usynlig magisk mann» som det Wetteland har.
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Holm, Sverre
(2021).
En anmeldelse av en innbilt bok.
Avisa Vårt land.
Show summary
LITTERATUR: Jeg skulle ønske at Vårt Land hadde anmeldt min bok «Den innbilte konflikten», heller enn å anmelde en innbilt bok om Guds eksistens og Bibelen.
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Holm, Sverre
(2021).
Hensikt eller tilfeldighet?
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Holm, Sverre
(2021).
Gode grunner til at naturvitenskap og Gud ikke er i konflikt.
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Holm, Sverre
(2021).
Abels forgård: Gud og gullkabler.
[Radio].
NRK P2.
Show summary
Dagens makker er professor i signalbehandling, og hisset for noen år siden på seg mektige krefter i NRK da han skrev om lydkvaliteten på DAB-radio.
Og i høst klarte han kunststykket å hisse på seg både ateister og konservative kristne med sin bok om forholdet mellom Naturvitenskap og Gud.
Ukas makker: fysikkprofessor Sverre Holm
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Holm, Sverre
(2021).
Fractionality in time-varying systems.
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Holm, Sverre
(2021).
Fractional wave equations appear naturally in complex media.
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Aparicio, Joaquin & Holm, Sverre
(2021).
Evaluation of acoustic ambient noise cross-correlations in indoor environments.
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Holm, Sverre
(2021).
Non-integer derivatives in selected areas of physics.
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Holm, Sverre
(2021).
Non-integer derivatives in acoustics and other areas of physics.
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Holm, Sverre
(2021).
Long delayed radio echoes – the illusive secret of the ionosphere.
Show summary
The first radio echoes with long delays were reported in 1927 by Jørgen Hals in Oslo, Norway on 9.54 MHz signals from the Netherlands. His first report exists at the National Library in Oslo and was later reported in Nature [Størmer, 1928]. Controlled experiments where delays ranged from 3 to 30 seconds confirmed the phenomenon and convinced most skeptics that the phenomenon was real [van der Pol, 1928]. About 15 different hypotheses have been presented over time for their cause [Shlionskiy 1985]. The five most likely ones will be presented here. They involve phenomena with long-distance travel such as around the world many times or reflection from plasma clouds. Another scenario is where the speed of propagation is substantially slower than normal as if there is mode conversion to mechanical waves in the ionosphere with or without nonlinearity [Vidmar, Crawford 1985]. The only one of the five which is understood well is when a signal is ducted in the magnetosphere and reflected from the opposite hemisphere. It may occur for frequencies up to 4 MHz and will give delays of up to 0.5 seconds. The further north, the longer the delay. Therefore, such medium delay echoes may sometimes be confused with round-the-world echoes of 138 ms, which however seldom occur at such low frequencies. There are examples of such echoes from Tasmania and St. Petersburg in the scientific literature. Amateur operator reports from New York, Georgia, California, Newfoundland, Denmark, and the UK [Martinez, 2007] from the last decades will be presented and analyzed and audio from some of them will be demonstrated. The delay is predictable from geomagnetic latitude using a simplified dipole model for the geomagnetic field line [Holm 2009]. The effect occurs during the dark hours and is most likely during winter months of years of low solar activity. A good report of such a phenomenon should involve a digital recording of audio using CW and not SSB signals. Delay measurement with amateur radio equipment is a challenge and needs to compensate for the usual delay between the onsets of the transmitter and sidetone signals.
View all works in Cristin
Published
Nov. 4, 2010 1:58 PM
- Last modified
Apr. 16, 2024 3:26 PM