In mid-September 2017, I noticed how lacking whistlers and any other ELF-VLF emissions were at my home-location in the northern Mojave Desert (except for sferics and tweeks from lightning-storms). When a series of geomagnetic storms hit Earth's Magnetosphere in mid-October 2017 with K-indices routinely reaching level-6, fine aurora in northern latitudes in the auroral-oval region such as Canada, Iceland and northern Scandinavia, I monitored natural-radio for the entire period (and I can do so 24/7 presently). I heard nothing but static/sferics/tweeks. Nothing else...
When I first began recording natural-radio back in 1991, even at S.F. Bay Area/Marin County geo-magnetic latitudes, K-indices above 4 would routinely cause "dawn chorus" to occur near and just after sunrise. If the K-index reached level 6, chorus was even quite strong in Marin County. Back then, whistlers were very common - the days when they occurred - even if just a few per hour - were the majority of days. Now in late 2017, I hear NO WHISTLERS - virtually none. Yes indeed--NOTHING!
That mid-October 2017 series of magstorm days when the K-index reached 6 for nearly 16 hours continuously at times, produced virtually NO emissions at my home location in the northern Mojave Desert. Nothing overall but /sferics/static/tweeks (pretty-sounding, anyway)... day after day, coming from my ELF-VLF receiver-to-FM transmitter "Relay" out in a hidden sandy/salt-grassy "island" in a low-AC-hum location out on the Owens (dry) Lakebed near Keeler, California, about 1 km from my home. The photo of this Relay is toward the end of "The VLF Story" on this site, or below at the footer of this statement.
I am not certain, however, if this huge reduction in natural-radio emissions has anything to do with the sub-auroral-zone visible-phenomenon called "Steve" - a thin, gray-white-banded/thready-looking quasi-auroral-form phenomenon that was discovered in (Alberta?) Canada only a few years ago (or perhaps just more "noticed" now thanks to modern very high-speed/fast ISO digital-camera technologies now available compared to the pre-digital/35mm-film days when I first began photographing aurora (in Saskatchewan and Alberta, Canada back in September 1993 with only (slow!) 100 ISO 35mm film for the lowest grain photos).
It is entirely possible that the growing amount of man-made "electromagnetic-smog" that ever-increases in field-strength and steadily-increases on higher and ever higher radio frequencies into the 'short-microwave' bands now, reaching over 500 GHz (and even 1 THz in some experiments in 2017). Man-made EM emissions in the 800 to 1600 MHz spectrum range have massively increased since the 1980s when cellular/mobile telephone technologies began - first in analoge form, then later morphing into PCM-digital transmissions in the late 90s. Ironically, perhaps the Internet itself is suppressing natural-radio emissions. Just a hunch... A massive amount/field-strength of digital-cell/mobile telephone/3G/4G radiate tangentially away from Earth (as these transmissions tend to be directed toward the horizon for max. coverage - they radiate then out tangentially into space, impacting the Magnetosphere and possibly altering or suppressing natural-processes in the magnetosphere. OR... the ionosphere itself - a longtime friend and radio DXer, Mike M. - whom introduced me to whistlers in 1988, nowadays complains that "propagation is awful" frequently. I agree, but it just can't be low-solar-fluxes keeping the ionosphere MUF low - it just has to be "something else." Previous "low-solar-flux periods in previous solar-minimum periods always elicited nice natural ELF-VLF emissions, but this year has been very strangely devoid.
Various military and civilian experiments with "Ionospheric Heaters" (such as the former HAARP that transmitted gigawatts of RF up toward the ionosphere) might have affected the ionosphere somehow. Perhaps in the future when the Sunspots return in large numbers and the 10.7 cm solar-flux reaches 200 again - maybe then will the frequent and glorious signals I once routinely recorded will return once again. For the time being though, it's going to be rather sparse overall.
To anyone whom has been a long-time natural radio listener such as Mike M. and myself, it's certainly not as rewarding to monitor natural ELF-VLF radio signals these days. We just monitor natural-radio during the big magstorms to see if the dead-silence is continuing or in case- something interesting does occur worth recording. Or, we just enjoy mere-static now, as that is often all there is to hear at mid-latitudes now except for the occasional whistler(s) and weak chorus being heard still. Since I myself am fascinated by the science behind lightning-storms, static/QRN is revealing, and night-time tweeks sound pretty.
But it is certainly not at all like the early 1990s, when I really ramped-up my recording and field-expedition efforts as my Internet Archives audio-albums present. Even in the deep-solar minimum during 1996 for example, natural ELF-VLF radio was WILD in Canada, and even great in California. I don't know about reception in Canada lately (since 2001 actually), but Iceland in December 2016 was nearly a "bust" in my observations - I would have thought I would have caught similar stuff as during my Canadian trips between 1993 and 2001, but everything I did hear was very weak - rather suppressed sounding... I cannot believe it is just due to low-solar activity. Fast-solar-wind streams via coronal holes produce big Earthly mag-storms still, but yet the Magnetosphere is rather quiet or even silent -- at least at ground-level. (SEE UPDATE: 22 January 2018 at the bottom of this page!)
Mike says: "The Magnetosphere is sick." I agree. Or it is it *possibly* the "also-sick" Ionosphere that might actually be "dampening" or even entirely "blocking" ELF-VLF emissions emanating from the Magnetosphere from reaching ground-level. Why this little theory of mine? The incredible EMFISIS stereo ELF-VLF satellites are "recording" wonderful phenomena/data up in low-Earth-orbit (LEO) but on the ground it has gone nearly silent, just like Rachel Carson's "Silent Spring" we're in a new, strange kind of "radio-silence" from the Magnestophere. Furthermore, studies of the NMP (north magnetic pole of Earth shows a now-quite rapid movement northward toward northeastern Siberia. Purportedly, data gathered by the SWARM satellites indicate a reduction of the magnetic-field over North America presently.
On 06 January 2018, in a conversation with my friend Kristjan in Reykjavik, Iceland, Kristjan mentioned that he read an article (TBA about the link) that the general background field-strengths of the global AC Mains Grid (and other man-made RF emissions as elaborated above?) might be contributing to a "bulging-out" of the Van Allen Belts surrounding Earth and thus the reduction. Fascinating, but portending some bad news there...
In closing, I hope listeners continue to observe natural-radio as I will continue on occasion in 2018 when I get the fancy and during the fewer large mag-storms forseen through the close-approaching solar-minimum, we need to see how long this might/will go on, and why this strange ELF-VLF silence is upon us now.
Stephen P. McGreevy - 07 January 2018 update.
UPDATE Monday 22 January 2018: It's not as silent as I thought as it was in the Autumn of 2017, which was very strange. During the weekend of 20-22 January 2018, we just went through another magnetic storm (Kp=7 max.) - this one was caused by a large coronal hole on the Sun facing Earthward that spewed out a fast solar-wind stream at over 600 km/sec or over 1.3 million MPH.
This hit a slow-solar-wind section, magnifying the plasma-impact upon Earth's Magnetosphere. Thus, early this morning at 0300 to 0530 PST / 1130 to 1330 UT on 22 January 2018, streams of whistlers occurred, but earlier at 0330 PST, I caught a nice doublet growler whistler while DXpeditioning at Dirty Socks Hot Springs 16 km from home as the radio signal travels - only one whistler cluster, but enough to listen at home... I arrived home at 1215 UT and listened/audio-recorded the whistler activity via the 87.9 MHz Relay pictured above, and I was very pleased to hear frequent one and two-hop near-pure and pure-tone whistlers! So things do occur, and thus research into the quantities of natural emissions must be ongoing throughout this coming solar-minimum. Certainly, these kinds of space-weather events do spawn nice whistler "events/openings" so I do encourage readers and listeners to keep at it all! This was very encouraging!
S.P. McGreevy on Monday 22 January 2018 update.