SAMPLE  LOWELL  IONOGRAM  INDEX

Electromagnetic waves propagating thru an ionized medium with a magnetic
field present (in this case, the earth's) are split into two components - the        
ordinary (o) and extraordinary (x) ray which usually have their own distinct
(though physically close) actual paths in the ionosphere.  The phenomenon is
known as birefringence (with an earth-bound analogy, of sorts, seen in the
optical behaviour of some crystalline minerals such as Iceland spar).  It is
a consequence of the two-root solution of the Appleton quadratic formula.  In
most propagation calculations only the o-ray is considered.

Over recent years I have often been asked to "explain" the digisonde traces.
The following samples are designed to illustrate a wide variety of phenomena
that are commonly seen on ionograms.  (Use the link near the bottom of this
page for a set of the more-current Lowell Digisonde ionograms.)



Oct 12, 1998 - 2330z
5Es echoes visible in this blanketing and non-blanketing Es sample


Dec 19, 1999 - 1615z
ionogram just slightly complicated by not only the 2F2 and 2Es echoes but
also the Es-F2 echo caused by the return of the outgoing pulse that had
already been once returned by Es to the earth and then repenetrated the Es


Jul 08, 1999 - 0200z
blanketing Es misleading automated digisonde into taking the Es-F echo for
h'F to calculate a too-low M-factor and so a too-low MUF


Feb 12, 2000 - 1900z
typical magnetic-storm supression of high-latitude foF2 along with increases
of h'F2 resulting in greatly-reduced F2 MUF's
(KBo: 5-5-6-7-5-4-4-2)


Oct 22, 1999 - 0850z
magnetic storm almost obliterating any F echoes at night with very
large h'F values creating small M-factors and thus very low MUF's
(KBo: 6-6-7-5-4-4-3-3)

a mix of multi-Es/F echoes with the Sep 22, 1999 magnetic storm
featuring auroral Es
(KBo: 3-2-3-4-4-3-5-6)
Sep 22, 1999 - 2215z
Sep 22, 1999 - 2310z


May 17, 2000 - 0615z
spread-F echoes typical of many nighttime magnetic disturbances
(The heavy Es levels are only incidental in this case.)
(KBo: 4-5-5-3-2-2-2-3)


Jun 18, 2000 - 1400z
nice example showing F1 and F2 layers, with their o and x-components
well separated by half the gyrofrequency at the height of reflection
(the cusp at foEp - penetration - is also easily visible near 3.5 MHz)


Jul 05, 2000 - 1307z
case of the automated digisonde mistaking the 2Es echo for the F2 echo and
so grossly miscalculating the M-factor from too low a h'F2 value and thus
the resulting excessively-high F2 MUF
(Many other far-worse examples have been come across!)


Nov 26, 2000 - 1645z
D-layer absorption from X4.0-flare, 1634-1648-1656, creating high fmin value
(5-min resolution NOAA GOES x-ray plots)


Dec 11, 2000 - 1530z
As a rule-of-thumb, the higher F2 MUF's will be generated by the F2 traces
that become and remain "horizontal" the longest before reaching the foF2
penetration value.
(But the lower h'F2 levels will also shorten the one-hop range!)


Jan 28, 2001 - 2200z
D/E-layer group-retardation effects on the low-frequency end of the F2-echo
more accentuated near "sundown" (at that height) giving a high "artifact" h'
value


Jan 29, 2001 - 1200z
the similar effect evident in the "pre dawn" sweep


Jan 31, 2001 - 2030z
more consequences of automation where one of the "blocked" segments of
the ionosonde sweep (to avoid QRMing occupants) is mistaken for foF2
and so produces a greatly-reduced calculated MUF

Assorted Chaos from the April 6-7, 2000 Magnetic Storm
(most notably auroral Es)
(KBo: 3-3-3-3-2-6-5-6 and 8-4-5-3-3-4-3-3)
Apr 06, 2000 - 1945z
Apr 06, 2000 - 2100z
Apr 06, 2000 - 2130z
Apr 06, 2000 - 2145z
Apr 06, 2000 - 2200z
Apr 06, 2000 - 2230z
Apr 06, 2000 - 2315z
Apr 06, 2000 - 2330z
Apr 07, 2000 - 0230z
Apr 07, 2000 - 0300z


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Page Created: January 27, 2001
Last modified: February 5, 2001