Return-Path: Received: from mtain-dd06.r1000.mx.aol.com (mtain-dd06.r1000.mx.aol.com [172.29.64.146]) by air-df04.mail.aol.com (v127_r1.1) with ESMTP id MAILINDF042-5eef4ba0a552245; Wed, 17 Mar 2010 05:48:03 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dd06.r1000.mx.aol.com (Internet Inbound) with ESMTP id D5F25380000B7; Wed, 17 Mar 2010 05:48:00 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Nrppy-00055u-0A for rs_out_1@blacksheep.org; Wed, 17 Mar 2010 09:46:50 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Nrppx-00055l-FX for rsgb_lf_group@blacksheep.org; Wed, 17 Mar 2010 09:46:49 +0000 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Nrppv-0002KJ-NV for rsgb_lf_group@blacksheep.org; Wed, 17 Mar 2010 09:46:49 +0000 Received: from abelian.netcom.co.uk (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by parrot.netcom.co.uk (Postfix) with ESMTP id EE3CE329224 for ; Wed, 17 Mar 2010 09:44:06 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by abelian.netcom.co.uk (8.13.1/8.13.1) with ESMTP id o2H9kf9e002315 for ; Wed, 17 Mar 2010 09:46:41 GMT Message-ID: <4BA0A501.5050506@abelian.org> Date: Wed, 17 Mar 2010 09:46:41 +0000 From: Paul Nicholson User-Agent: Thunderbird 2.0.0.14 (X11/20080421) MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: In-Reply-To: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: Ionospheric VLF propagation Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.2 required=5.0 tests=FROM_ENDS_IN_NUMS,ORDER_NOW autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G x-aol-sid: 3039ac1d40924ba0a5504e1f X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) Alexander wrote: > Certanly exponential factor exp(-r/a) should be present. > I mentioned this before. 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 mentioned in some literature but I have to follow that up. Assuming that, we have the estimate for daytime flux density at range r:- B = sqrt( 9.5e-21 * ERP/r) * exp( -r/2.9e6) > But this should be calculated. At the earth bondary one can > use Leontovich bondary condition Yes. > But what to do with ionosphere boundary... To neglect dissipation > in ionosphere looks not reasonable. Yes too. The ionosphere boundary is more complicated. There are two values for the refractive index - attenuation depends on direction relative to Earth's magnetic field. The result is phase and polarisation changes. I have some references to follow up here too. But it is complicated and time consuming. It would be nice to just use average figures for day and night attenuation - surely good enough for 'amateur' work. > To solve the problem (rather volumable problem) is nice task > for physicist. The hard work was done, decades ago, and appears to be fairly well established. But it is a major job to go through the literature and pick out what is relevant. It is a heady mix of plasma physics, EM theory and ray tracing. There are one or two textbooks - one I will order today. -- Paul Nicholson --