Firming up space weather connections and the magneto- acoustic phenomenon commonly referred to as the Hum
By Dr Chris Barnes, Bangor Scientific Consultants
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A link between Hum intensity and periods when the IMF ( Interplanetary Magnetic Field) swings southwards is established. This is consistent with the author's previous findings on the behaviour of the Hum and elctrojet indices. A space weather connection with the Hum supports it to be either a natural or anthropogenic phenomenon but the weight of evidence still points mainly at interactions involving World power systems.
The Hum is an enigmatic acoustic phenomenon first reported in Britain in the 1970’s and later in the USA in the early 1990’s. Hearers of the Hum usually report hearing a noise like a distant idling engine and usually although not exclusively in the night when it is extremely quiet. Some also report the noise as being difficult to screen out even using ear plugs and therefore capable of causing sleep deprivation, general annoyance and anxiety. There would appear to more outbreaks of the Hum being reported throughout the World in recent times so its emergence would appear in some way to map infrastructure development.
The present author, his wife, his sister-in law and occasionally his son are all hearers of the Hum. Thus all the studies made by the present author have a subjective element but have not required anecdotal input from unknown or unreliable third parties. The author loosely describes the Hum in the North Wales region as the Bangor Hum. It would seem it has all the characteristics of hums reported anecdotally around the World. It would not then seem too unreasonable to propose extension of hypotheses concerning the Bangor Hum to those more generally.
There is huge and often heated debate on Hum forums concerning the cause(s) of the Hum. Some cases of the Hum have been solved. Kokomo, for example, comes to light as an example thought to involve anthropogenic acoustic and infrasonic noise. Following this lead, some groups in the USA are convinced that the Hum is due to high pressure gas mains. Some groups in both the USA and UK believe the Hum to have an electro-acoustic connection and, perhaps, be related in some way to Tetra masts. However, since the Hum pre-dates these and the demodulated waveforms do not correspond with what is heard it may be fairly safe to dismiss this cause.
After very extensive studies the present author has come to conclusion that at least for the Hum in Bangor and possibly World Wide the most likely main culprit in the Hum is the interaction with the World’s electricity grids and the Earth’s space weather environment. That is not to say however that the space weather environment would not or could not alter the propagation characteristics of virtually any airborne or ground borne noise, anthropogenic or otherwise, due to magnetosphere-atmosphere-lithosphere interactions. Since the Hum can be dependent on room or building resonance and is a very subjective phenomenon it must not be forgotten that more than one driver could potentially produce the same or very similar psycho acoustic sensations.
The author has recently shown that when the IMAGE electrojet indices IL and IU approach one another and zero, the Hum in Bangor maximises. It has also very recently indeed been shown that electrojet currents tend to minimise only in darkness when the interplanetary magnetic field (IMF) swings southward partially cancelling out the Earth’s magnetic field, http://www.ann-geophys.net/28/1167/2010/angeo-28-1167-2010.pdf
In order to firm up the connection between space weather and the Hum it was decided to see what if any correlation there is between relative Hum intensity and instances of the IMF ( Bz ) being southwards facing.
Experimental and Results
The experiment is very simple, Retrospective data for the subjective Hum intensity in Bangor months of September and October 2010 had been recorded in diary form by the present author. Only those data from still days (no significant wind) were used as it has previously been shown that winds of certain speeds can blow out the coherence of the Hum. The subjective Hum levels were recorded as four discrete values on a scale of 0-10. Where 10 = intolerable levels even with wax ear plugs; 7 = Hum bad enough to need ear plugs. 4= Hum which could be lost simply by burying one’s heads in a pillow and finally where 0= no Hum at all. The number of days each value occurred was recorded and then the percentage of these days when the IMF was south was also calculated. The results are plotted in figure 1.
The results, figure 1, clearly shows that for increasing Hum level the expectation is that the IMF will be southward as predicted. That is not to say Hum won’t be experienced when the IMF is northwards but simply that the probability of very intense Hum is much greater with the IMF southward.
Conclusions and further work
It is concluded that at least for the Hum in Bangor this maximises when the IMF ( Bz) is Southwards. Because no one absolute cause of the Hum has been proven by measurement there is recent talk on internet Hum forums of the Hum as a possible natural phenomenon. Now we have a confirmed Space Weather influence this could support either a natural or anthropogenic phenomenon interacting or interfering with space weather and/or having earthbound or earth locked propagation is a function of the same. Certainly it is accepted that infrasound pressure pulses arise from both aurora and electrojets in general
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1547494 and the author has measured infrasound during occurrences of the Hum. In previous publications the author has shown a strong link between the arrival of the Hum and power line harmonic radiation. The behaviour of power line harmonic radiation and its associated magnetic line resonance is still not that well understood as world wide phenomena. However, it has recently been shown that signals emitted from a pulsed Horizontal Electric Dipole (HED) at certain locations near the dip-equator can drive an artificial electrojet in the ULF/ELF range. Naturally there is military interest in such technologies both for submarine communication and underground tomography studies, http://adsabs.harvard.edu/abs/2008AGUFMSA42A..01P. Thus some on Hum forums have blamed HAARP and similar technologies for the Hum. However the Hum predates these technologies. Perhaps less obvious to amateur Hum researchers but now blindingly obvious to the present author is that power lines radiating pulsed harmonics and acting a Beveridge antennas are indeed wholly analogous to the HEDS referred to in the above reference. So this may account for more and more regions of the World starting to experience the Hum as technically and infrastructure spread particularly in equatorial regions.
The author is presently compiling research into time series analysis of the Hum in Bangor and hopes to report on this in the very near future. Early indications are that this analysis, as excepted, is consistent with the Hum as an anthropogenic rather than natural phenomenon.
J.W.Gerjerloev et al, Response of the Auroral Electrojet Indices to abrupt Southward IMF turnings, Ann Geophys 28, 1167-1182, 2010, http://www.ann-geophys.net/28/1167/2010/angeo-28-1167-2010.pdf
J.; Jabor, A.; Liszka, L.; Eide,
A.J.; Lindblad, T.; Bergkvist, L.P.N.-O.;
Stahlsten, T.; Andersson, B.L.; Karasalo,
I.; Cederholm, A.;
Gavle Univ. ,Filtering and extracting features from infrasound data, This paper appears in: Real Time Conference, 2005. 14th IEEE-NPSS
Issue Date: 10-10 June 2005 On page(s): 5 pp. Location: Stockholm
Print ISBN: 0-7803-9183-7 INSPEC Accession Number: 9072241
Digital Object Identifier: 10.1109/RTC.2005.1547494
Papadopoulos, K. ,Pulsed Artificial Electrojet Generation, http://adsabs.harvard.edu/abs/2008AGUFMSA42A..01P