Topband: Poor Propagation On 160

[KN4LF, Thomas Giella]

DF2PY Said:
As the last days,despite low WWV numbers, yielded almost no DX to North
America  i tried to check with magnetograms along the suspected route of
signals......

Thomas KN4LF Says:
The poor 160 meter band conditions as of late, even with low A/Ap and K/Kp
values, is due to polar cap absorption and polar radio blackouts. Polar cap
absorption and polar radio blackouts are caused by high energy protons
arriving via a solar flare. These high energy protons emitted in a solar
flare create the auroras we see and the overionization of the D layer and
therefore absorption of high latitude path broadcast band and 160 meter
radio signals. End result, what we call auroral conditions, when high
latitude paths are basically dead but low latitude paths from the Caribbean
and Central and South America are predominate. As the A/Ap and K/Kp values
are tied to geomagnetic disturbances and ionospheric storms, these events
basically tear up the F layer only and affect the higher shortwave
frequencies only, not the E layer which is the predominate propagation layer
for 160 meter propagation. Low A and K values can fool you into thinking
high latitude conditions on the broadcast band and 160 should be good.
Forget the A and K indices for 160, you have to look at the proton flux
values at http://sec.noaa.gov/rt_plots/pro_3d.html . If the levels are at
and above 10 Mev then there is going to be high absorption of 160 meter
signals by the D layer on high latitude paths and skewed propagation paths,
as the transmitted 160 meter signal seeks a path of least resistance or a
more southerly path. This has been the case repeatedly so far this fall,
with many X class solar flares and we have been above the 10 Mev proton
level for many days at a time.

POLAR CAP ABSORPTION (PCA).  An anomalous condition of the polar IONOSPHERE
          whereby HF and VHF (300- 3000  khz) radiowaves are absorbed, and

LF and VLF (3 - 300 khz) radiowaves are reflected at lower altitudes
          than normal.  In practice, the absorption is inferred from the
          proton flux at energies greater than 10 MeV, so that PCAs and
          PROTON EVENTs are simultaneous.  Transpolar radio paths may still
          be disturbed for days, up to weeks, following the end of a proton
          event.

PROTON.   Solar activity levels with at least on high energy event (Class X
          Flares)

PROTON EVENT.  By definition, the measurement of at least 10
          protons/sq.cm/sec/steradian at energies greater than 10 MeV.

PROTON FLARE.  Any FLARE producing significant FLUXes of greater-than-10 MeV
          protons in the vicinity of the earth.

http://www.windows.ucar.edu/spaceweather/polar_com.html

73,
Thomas Giella, KN4LF

Plant City, FL
Grid Square- EL88wx
CQ Zone 5
ITU Zone 8

Email: kn4lf@tampabay.rr.com

KN4LF 160 Meter Amateur Radio Resources  And More:
http://www.kn4lf.com




---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.295 / Virus Database: 159 - Release Date: 11/1/01