..... I found in another paper a formula for field strength at VLF. It uses Legendre functions to model propagation in terms of cavity modes, combined with an empirical model of attenuation. Formula
Sorry, that should have been Pure and applied geophysics, (volume price $110, single articles a mere $34! I can get copies through the British Library but it takes weeks). It's a challenge - those Le
It is one point yet. Let's wait for 3-4 at least. True, true. I am familar with such problems but mainly in condensed matter (particulary magneto-optics) not in plasma physics. But electrodynamics it
This would be the most straightforward explanation for the high signal strength. The signal expands with 1/r^2 power density and 1/r field strength until it is constrained by the Earth-ionosphere cav
Certanly exponential factor exp(-r/a) should be present. I mentioned this before. But i have no ideas how to estimate roughly (at least) parameter (length) a. Intuitively i expect a = few of 1000s km
Dear Markus, your calculations are fully adequate only while ionosphere does not work. I.e. for less then about 100 km (very approximative). At 180 km and 800 km ionosphere influence is certanly wort
Dear LF, on the phone, Stefan mentioned that he was running about 0.4 A into the nearly vertical (70°), 100 m long kite antenna. Thus radiated power would be EMRP = 1579 ohm * (0.4 A * sin(70°) * 50
Yes you did! I am following your lead with this 1/sqrt(r) thing and the exponential factor. And it is working - it is giving the right answer for Stefan's signal! 3dB per 1000km (daytime) is mentione
By the way it is very close to estimation: E(800km) ~ E(100km)*sqrt(100km/800km) where E(100km) calculated without ionospere, as you, Markus, calculated. Certanly it is very rought formala. Up to the
This would be the most straightforward explanation for the high signal strength. The signal expands with 1/r^2 power density and 1/r field strength until it is constrained by the Earth-ionosphere cav
I've been reading up about the Austin-Cohen formula, originally an empirical determination, valid only for long waves (> 200m): signal strength proportional to exp( -alpha * r/sqrt(lamda)) where alph
That's a step forward. Up to now we've tried B = sqrt( 9.5e-21 * ERP/r) * exp( -r/a) where a = 2.9e6 for daytime path, or 4.3e6 for nighttime path. This assumes radiated power is spread uniformly ove
It's a challenge - those Legendre functions with complex parameters... there's an expression involving hypergeometric functions and some code for that in 'Numerical Recipes in C', either that or (ve
Dear ultra-lowfers, why not Mathematica? It is a very powerful tool containing all special functions you need (e.g..: Legendre). No recipes, no subroutines, no Fortran... Best regards Antonio -- Orig
