https://hfunderground.com/wiki/index.php?title=Talk:Ionosonde&feed=atom&action=historyTalk:Ionosonde - Revision history2024-03-28T18:42:52ZRevision history for this page on the wikiMediaWiki 1.16.5https://hfunderground.com/wiki/index.php?title=Talk:Ionosonde&diff=4195&oldid=prevStrange Attractor: Replacing page with '==Additional text=='2010-09-06T07:47:01Z<p>Replacing page with '==Additional text=='</p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==Additional text==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==Additional text==</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del style="color: red; font-weight: bold; text-decoration: none;"></del></div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del style="color: red; font-weight: bold; text-decoration: none;">As the frequency increases, each wave is refracted less by the ionisation in the layer, and so each penetrates further before it is reflected. As a wave approaches the reflection point, its group velocity approaches zero and this increases the time-of-flight of the signal. Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency (fo) just exceeds the peak plasma frequency of the layer. These frequencies are identified by the layer where reflection takes place (foE, foF1, foF2 and foEs). In the case of the extraordinary wave, the magnetic field of the earth enhances the reflection capability of the ionosphere and reflection occurs at a frequency (fx) that is higher than the ordinary wave by half the electron gyrofrequency.</del></div></td><td colspan="2"> </td></tr>
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<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del style="color: red; font-weight: bold; text-decoration: none;">The frequency Fc at which a wave just penetrates a layer of ionisation is known as the critical frequency of that layer. The critical frequency is related to the electron density of the specific layer (D, E, F1 or F2).</del></div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del style="color: red; font-weight: bold; text-decoration: none;"></del></div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del style="color: red; font-weight: bold; text-decoration: none;">All transmitted frequencies above this critical frequency will penetrate the layer without being reflected. Their group velocity will however, will be slowed by any ionisation, and this will add to the time-of-flight. If such a wave encounters another layer, whose plasma frequency is higher than the frequency of the wave, it will be reflected, and the return signal will be further delayed as it travels back through the underlying ionisation. Therefore, HF frequencies between 5 and 30 MHz pass through the E layer and are reflected at the F layer. Similarly, MF frequencies (AM broadcast stations) at night pass through the D layer and are reflected by the E layer.</del></div></td><td colspan="2"> </td></tr>
</table>Strange Attractorhttps://hfunderground.com/wiki/index.php?title=Talk:Ionosonde&diff=4193&oldid=prevStrange Attractor at 07:43, 6 September 20102010-09-06T07:43:49Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==Additional text==</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>==Additional text==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>As the frequency increases, each wave is refracted less by the ionisation in the layer, and so each penetrates further before it is reflected. As a wave approaches the reflection point, its group velocity approaches zero and this increases the time-of-flight of the signal. Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency just exceeds the peak plasma frequency of the layer. In the case of the extraordinary wave, the magnetic field <del class="diffchange diffchange-inline">has an additional effect, </del>and reflection occurs at a frequency that is higher than the ordinary wave by half the electron gyrofrequency.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>As the frequency increases, each wave is refracted less by the ionisation in the layer, and so each penetrates further before it is reflected. As a wave approaches the reflection point, its group velocity approaches zero and this increases the time-of-flight of the signal. Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency <ins class="diffchange diffchange-inline">(fo) </ins>just exceeds the peak plasma frequency of the layer<ins class="diffchange diffchange-inline">. These frequencies are identified by the layer where reflection takes place (foE, foF1, foF2 and foEs)</ins>. In the case of the extraordinary wave, the magnetic field <ins class="diffchange diffchange-inline">of the earth enhances the reflection capability of the ionosphere </ins>and reflection occurs at a frequency <ins class="diffchange diffchange-inline">(fx) </ins>that is higher than the ordinary wave by half the electron gyrofrequency.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>The frequency at which a wave just penetrates a layer of ionisation is known as the critical frequency of that layer. The critical frequency is related to the electron density <del class="diffchange diffchange-inline">by </del>the <del class="diffchange diffchange-inline">simple relation;</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>The frequency <ins class="diffchange diffchange-inline">Fc </ins>at which a wave just penetrates a layer of ionisation is known as the critical frequency of that layer. The critical frequency is related to the electron density <ins class="diffchange diffchange-inline">of </ins>the <ins class="diffchange diffchange-inline">specific layer (D, E, F1 or F2).</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">F_c = 8.98*sqrt(Ne) for the ordinary mode.</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div>All transmitted frequencies above this critical frequency will penetrate the layer without being reflected. Their group velocity will however, will be slowed by any ionisation, and this will add to the time-of-flight. If such a wave encounters another layer, whose plasma frequency is higher than the frequency of the wave, it will be reflected, and the return signal will be further delayed as it travels back through the underlying ionisation. <ins class="diffchange diffchange-inline">Therefore</ins>, <ins class="diffchange diffchange-inline">HF frequencies </ins>between <ins class="diffchange diffchange-inline">5 </ins>and <ins class="diffchange diffchange-inline">30 MHz pass through </ins>the <ins class="diffchange diffchange-inline">E layer and are reflected at </ins>the <ins class="diffchange diffchange-inline">F layer</ins>. <ins class="diffchange diffchange-inline">Similarly, MF frequencies (AM broadcast stations) at night pass through </ins>the <ins class="diffchange diffchange-inline">D layer and are reflected by the E layer</ins>.</div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">and</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">F_c = 8.98*sqrt(Ne) + 0.5*Be/m for the extraordinary mode.</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div> </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div><del class="diffchange diffchange-inline">Here F_c is the critical frequency in Hz, Ne is the electron concentration per metre cubed, B is the magnetic field strength, e is the charge on an electron and m is the mass of an electron.</del></div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div> </div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
<tr><td class='diff-marker'>-</td><td style="background: #ffa; color:black; font-size: smaller;"><div>All transmitted frequencies above this critical frequency will penetrate the layer without being reflected. Their group velocity will however, will be slowed by any ionisation, and this will add to the time-of-flight. If such a wave encounters another layer, whose plasma frequency is higher than the frequency of the wave, it will be reflected, and the return signal will be further delayed as it travels back through the underlying ionisation. <del class="diffchange diffchange-inline">The apparent</del>, <del class="diffchange diffchange-inline">or virtual height indicated by this time delay will therefore be greater than the true height. The difference </del>between <del class="diffchange diffchange-inline">true-height </del>and <del class="diffchange diffchange-inline">virtual height is governed by </del>the <del class="diffchange diffchange-inline">amount of ionisation that </del>the <del class="diffchange diffchange-inline">wave has passed through</del>. <del class="diffchange diffchange-inline">Recreating </del>the <del class="diffchange diffchange-inline">true-height profile of electron concentration from ionogram data is an important use of ionosonde data. Such a procedure is known as true height analysis</del>.</div></td><td class='diff-marker'>+</td><td style="background: #cfc; color:black; font-size: smaller;"><div></div></td></tr>
</table>Strange Attractorhttps://hfunderground.com/wiki/index.php?title=Talk:Ionosonde&diff=4192&oldid=prevStrange Attractor: New page: ==Additional text== As the frequency increases, each wave is refracted less by the ionisation in the layer, and so each penetrates further before it is reflected. As a wave approaches the...2010-09-06T07:36:44Z<p>New page: ==Additional text== As the frequency increases, each wave is refracted less by the ionisation in the layer, and so each penetrates further before it is reflected. As a wave approaches the...</p>
<p><b>New page</b></p><div>==Additional text==<br />
<br />
As the frequency increases, each wave is refracted less by the ionisation in the layer, and so each penetrates further before it is reflected. As a wave approaches the reflection point, its group velocity approaches zero and this increases the time-of-flight of the signal. Eventually, a frequency is reached that enables the wave to penetrate the layer without being reflected. For ordinary mode waves, this occurs when the transmitted frequency just exceeds the peak plasma frequency of the layer. In the case of the extraordinary wave, the magnetic field has an additional effect, and reflection occurs at a frequency that is higher than the ordinary wave by half the electron gyrofrequency.<br />
<br />
The frequency at which a wave just penetrates a layer of ionisation is known as the critical frequency of that layer. The critical frequency is related to the electron density by the simple relation;<br />
<br />
F_c = 8.98*sqrt(Ne) for the ordinary mode.<br />
and<br />
F_c = 8.98*sqrt(Ne) + 0.5*Be/m for the extraordinary mode.<br />
<br />
Here F_c is the critical frequency in Hz, Ne is the electron concentration per metre cubed, B is the magnetic field strength, e is the charge on an electron and m is the mass of an electron.<br />
<br />
All transmitted frequencies above this critical frequency will penetrate the layer without being reflected. Their group velocity will however, will be slowed by any ionisation, and this will add to the time-of-flight. If such a wave encounters another layer, whose plasma frequency is higher than the frequency of the wave, it will be reflected, and the return signal will be further delayed as it travels back through the underlying ionisation. The apparent, or virtual height indicated by this time delay will therefore be greater than the true height. The difference between true-height and virtual height is governed by the amount of ionisation that the wave has passed through. Recreating the true-height profile of electron concentration from ionogram data is an important use of ionosonde data. Such a procedure is known as true height analysis.</div>Strange Attractor