About
Sporadic E
Sporadic
E is an unpredictable natural phenomenon the occurs in the E region of
the ionosphere. This phenomenon is best known to hobbyists by the
resultant radio wave propagation that occurs.
While sporadic E is unpredictable, numerous correlations and observations have been made, by amateurs and scientists alike. For example, sporadic E is known to have a diurnal pattern, peak near the solstices, and occur more frequently in latitudes closer to the equator. Other facts are well documented as well, such as ionization densities, types of ions responsible, altitude of the ionized "clouds", etc.
In trying to understand the causes of sporadic-E, scientists and amateurs have tried to draw numerous correlations and build supporting thoeries. These have ranged from weather related catalyst theories, to ionospheric windshear (still a leading theory), to other astronomical impacts (meteors, comets, the moon's gravity, etc). None of the directly measureable theories have held up even close to 100% of the time under test, and just when we think we're starting to understand sporadic-E, it will surprise us with unanticpated behavior.
Thousands of observations and studies have been documented in scientific journals and amateur radio periodicals. In fact, in the 1970's several sessions were held among the univeristy community (Seminar on the Cause and Structure of Sproadic E). Some of these studies are highly scientific, and some less so. Some of the theories proposed seem highly improbable. This page is meant to be a reference to those online resources surrounding the study and occurrence of Sporadic E.
For more information, check out the links below, and for a primer of Sporadic E, check these documents:
Sporadic-E
Propagation at VHF: A Review of Progress and Prospects,
by E. Pocock, W3EP
A
7 Year Study of 50MHz Sporadic-E Propagation
by Pat Dyer, WA5IYX
Mid-Latitude
Sporadic-E - A Review by Michael Hawk - hawk@amfmdx.net
Sporadic
E Links
Numerous
research papers covering the ionosphere and sporadic-E exist online - too
many to list here. The papers below are those which I have found
use in, are currently "hot topics" in the field, or newly posted online.
Listing here does not necessarily mean that the maintainer of this web
page agrees with the findings or assumptions.
If you are aware of any other papers that you think are unique or of general interest, feel free to pass the link along to me, hawk@amfmdx.net.
Meteorlogical
Effects in the Ionosphere: A Review (1995 - Geomagnetism
and Aeronomy)
Long
Term Variations of Sporadic E Layers over Fortaleza, Brazil
(1996 - Ionosonde Network Advisory Group)i
Sporadic-E
and Sudden Neutral Layers (March 1996)
Study
of Sporadic-E Clouds by Backscatter Radar (May 1996, Annales Geophysicae)
[PDF]
Cometary
Origin of Sporadic E (July 1996 - Annual Meeting
of the Society of Amateur Radio Astronomers)
Decameter
mid-latitude sporadic-E irregularities in relation with gravity waves
(February 1997, Annales Geophysicae) [PDF]
The
Influence of the Semi-Diurnal Tide on Altitude Variations of the Sporadic-E
Layer (April 1998 - International Journal of
Geomagnetism and Aeronomy)
A
Discussion on the Cometry Origin of Sporadic E
(May 1998 Six News)
Recent
Research Activities in the Lower Ionosphere at Arecibo
(late 1990's - Arecibo Observatory)
Modeling
and Mapping Sporadic E Using Backscatter Radar (Nov, 1999, R.J. Norman,
P.L. Dyson and J.A. Bennett
A
Role of Neutral Motions in Formation of Midlatitude E-Region Field-Aligned
Irregularities (Jan 2000 - Geophysical Research
Letters)
Ion
Layer Separation and Equilibrium Zonal Winds in Midlatitude Sporadic E
(Feb 2000 - Geophysical Research Letters)
On
the Spectrum of Mid-Latitude Sporadic-E Irregularities
(May 2000 - Annales Geophysicae)
Meteor
Trail Advection Observed During the 1998 Leonid Shower
(July 2000 - Geophysical Research Letters)
Comments
on "Modelling the peak of the ionospheric E layer" by J. E. Titheridge
(2001 - Arecibo Observatory)
OFFLINE
RESOURCES
I
consider the following to be must-reads on the subject of sporadic-E.
Many resources are only available in print versions at your local academic
library, so if you have a chance, check out these titles:
Science
and Radio Periodicals Articles and Research
listed
in chronological order
Thomas,
J.A. and Smith, E.K., A survey of the present knowledge of sporadic-E
ionization, Journal of Atmospheric and Terrestrial Physics, 13, 295-314,
1959
Whitehead,
J.D., The formation of the sporadic-E layer in the temperate zones,
Journal of Atmospheric and Terrestrial Physics, 20, 49-58, 1961
Whitehead,
J.D., Difficulty Associated with Wind-Shear Theory of Sporadic E,
Journal of Geophysical Research, 76, 3127-3135, 1971
Whitehead,
J.D., On the peculiar shape of sporadic-E clouds, Journal of Atmospheric
and Terrestrial Physics, 40, 1025-1028, 1978 Smith,
E.K., Temperate zone sporadic-E maps (foEs 7 MHz), Radio Science,
13, 571-575, 1978
Whitehead,
J.D., Recent work on mid-latitude and equatorial sporadic-E, Journal
of Atmospheric and Terrestrial Physics, 51, 401-424, 1989
Pocock,
E and Dyer, P.J., Eleven Years of Sporadic E, QST, 23-28, March
1992
Mathews,
J.D., Sporadic E: current views and recent progress, Journal of
Atmospheric and Solar-Terrestrial Physics, 60, 413-435, 1998
JD Whitehead is one of the leading researchers in Sporadic E. A list of his publications is here.Most are only available at academic libraries.
View a list of additional print resources I've used in past research.
Books
Worldwide
Occurrence of Sporadic E - Ernest K. Smith National Bureau of Standards
Circular 582, March 15, 1957 - Historic book documenting Dr. Smith's Ph.D.
thesis at Cornell University
Beyond
Line of Site
- Edited by Emil Pocock, W3EPARRL, October 1992 - Compilation of studies
of VHF propagation from the pages of QST magazine
The following are sources of background information, tangentially related papers, or real-time data sources.
Online
Digisondes and Ionosondes
Ionospheric
Variables Explained (CHARS type)
Ionospheric
Storms - A Review (1999, MIT)
Red
Sprites and Blue Jets - a few people believe
these events may be a catalyst in sporadic-E formation
SEC
Space Weather - Space Environmental Center latest
updates