http://59.160.210.74:8080/jspui/bitstream/123456789/454/1/VLF%20signals%20in%20summer.pdf
(Bose National Centre for Basic Sciences)
http://www.ursi.org/proceedings/procGA11/ursi/GP2-15.pdf
Paul,
I?m sending this
link because the data seems unusual. I thought it might come in handy if
something of this sort appears in efforts within this group; but I am not
inclined to have confidence in the results of the attached unless I happen to
run across similar independent results (and I did not, in my search last
week). So, I?m planning to just file the attached but thought you might want
to see it because it?s interesting if not well-supported by other studies.
Plots* in the link
below show an interesting distribution of VLF broad daytime amplitude maxima
that are (a) greater than, or (b) less than nighttime
maxima.
The study used a
single transmitter (18.2 kHz), and receivers at distances from 500 km to ~
3,000 km, with two-week collections in summer and
winter.
I tried to correlate
(a) or (b) (daytime maxima greater than or less than nighttime maxima) with
distance or bearing and did not find a reasonable
correlation.
In winter 3 of 9 RX
stations had daytime amplitude (broad) maxima greater than nighttime
maxima.
In summer 3 of 12 RX
stations had daytime amplitude (broad) maxima greater than nighttime
maxima.
Winter ?day maximum
minus night maximum? (averaged over 2 weeks) ranged (by RX station) from +20
dB to -11 dB, with 6 of 9 RX stations on the - side; the winter average of all
RX stations seemed to be around -0.5 dB
Summer ?day maximum
minus night maximum? (averaged over 2 weeks) ranged (by RX station) from +8 dB
to -10 dB, with 9 of 12 RX stations on the - side; the summer average of all
RX stations seemed to be around -2 dB
The wide range of
?day maximum minus night maximum? results (by RX station), together with the
absence of any apparent correlation with distance or bearing, makes this data
seem unusual. Well, maybe not for LF/VLF.
* Figure 3 and
Figure 7
73, Jim
AA5BW
