23 August 2011

How People in Science See Each Other

Found this little gem here. Thanks Steve.


19 August 2011

Lightning and TGF Statistics


My favourite slide from my URSI 2011 presentation in Istanbul. The idea was to contrast the frequency of TGFs and lightning as well as reflect the degree of correlation between TGFs detected on RHESSI and lightning data from the World Wide Lightning Location Network (WWLLN). Basically WWLLN sees around 10% of global lightning and we have managed to link around 10% of the RHESSI TGFs to WWLLN lightning locations. Anyway, I like the simplicity of the graphic.

06 August 2011

Wedding Speech

On the morning of his wedding Charles pointed out to me that “a wedding is not like going to the dentist”. I am still not quite sure what he meant, but I do know that he is entirely correct.

My wife and I (… I have been waiting some time to say that!) have a number of people we would like to thank.
  1. We would like to thank Malcolm and Veronica for their generosity with this wedding. Thank you for allowing me to marry Claire. If I had never met her, I would be a poorer man. Thank you for bringing up such a fine young lady and supporting her in everything that she has chosen to do.
  2. Mom and Dad, thank you for the beautiful flowers and magnificent wedding cake as well as for sewing the tablecloths. Thank you for being such good friends to Claire and always being ready to have her over for dinner and a good chat. Thank you also for the example you have set: I aspire to have a marriage like yours.
  3. We are also very grateful to Dave, Troy and Fiona, Struan and Jolene, and Christine and Zak who have travelled a long way to share this day with us.
  4. Jody thank you for being a fabulous best friend to Claire and the most organised matron of honour in the world. You have made this wedding so exciting for her and helped her plan it the whole way from the dress to the decorating.
  5. Talitha thanks for cleaning Claire up today. Charlie, you have been a source of advice on everything from robotics to relationships. See what I did there? Bit of alliteration? There’s more of that later. Thanks also for not hesitating to tell me when I am wrong.
  6. Troy, dude, we go back a long way. Thanks for always being around. Troy is the most creative person I know. In fact, he makes things up for a living. I am sure that there will be some fanciful stories in his speech. I thank you for humouring him.
I would like to mention a few people who could not be with us today and whose presence we miss:
  • Claire, Gavin and Dylan Joubert
  • Sandy, Angelique and Bernice Dewar
  • Heather Fox (Dave, we are very glad that you could still be with us!).
I believe that concludes the formalities.

Where is my cousin James...? James I am about to impart some relationship advice distilled and refined over many years. Take note, because this is gold. When you meet a girl, the most important thing is to ensure that she remembers you the next day. You need to stand out above the competition. And this is why on the evening that I met Claire I skillfully contrived to spill an entire glass of red wine into her lap. I could be 100% certain that the next morning, when she was soaking her clothes, there was no doubt in her mind about who was responsible. The fact that Claire is now Mrs Collier is testimony to the success of this technique.
In Latin the name Claire means “bright shining girl”. And I think that you will agree with me that this could not be a more apt description. I do not know anyone more animated or vivacious. And that is just the tip of the iceberg.
  • She is independent, funny, positive, thoughtful and devoted.
  • Claire is caring yet carefree. She has a particular soft spot for the downtrodden and dispossessed. This was vividly brought home to me when she donated my entire stock of tinned bully beef and vintage running t-shirts to the homeless.
  • Claire is devastatingly smart. A brief conversation with her will make this apparent. However, I will illustrate with a story. A week or so ago we were driving back from the bluff and, in the course of conversation, I happened to alliterate a series of three words. I forget exactly what they were, but I was quite pleased with myself. I pointed out that alliterating four words would be pretty challenging. After a moment's consideration Claire responded with "Bikers bring their bitches to braais on the bluff" and a moment later went further with "Butch bikers bring their big bitches to boozy braais at brighton beach on the bluff". At that point I changed the subject.
  • Claire is unfailingly supportive. Ladies and gentlemen, I present Exhibit A. This sight is to be seen at various locations between Durban and Pietermaritzburg around the end of May each year. What starts out as a cute distraction on the side of the road gets transformed into something positively angelic as the day progresses. I know that I have Claire's full support in everything I do, regardless of how foolish they might be.
  • Claire enjoys cleaning. To an extent that borders on an obsession. She has a very close relationship with her washing machine. Were it not strictly platonic, I believe I might be quite jealous. She also believes that there are very few problems which cannot be solved by Mr Muscle. And, no, I am not “Mr Muscle”. Claire is also rather fond of vacuuming with her IPOD attached, belting out tunes at the top of her voice. Tunelessly. Not only tunelessly, but sometimes she gets the words wrong. I am sure that you are all familiar with GnTs. Perhaps you have heard of GnCs? I certainly never had. Apparently you dig for them. But you'll have to ask Claire for the details.
  • Now I am not quite as gregarious as Claire. In fact, my failure to dance causes Claire acute embarrassment. Perhaps we can elevate this embarrassment to a whole new level. <These Arms of Mine>.
Will you please join me in a toast. It has been said that the consumption of alcohol may create the illusion that you are tougher, smarter, faster and better looking than most people. Every minute I spend with Claire makes me feel that way. To Claire!

I suspect that after Claire's kitchen tea, some of the ladies here might be wondering whether I have deviated from my conventional mode of underwear for this momentous occasion. Well, I am happy to tell you... that you can just keep on wondering.

03 August 2011

Dental Panorama

I am a big fan of panoramic photography, and this just makes a visit to the dentist so cool.


02 August 2011

Signal Induced by Lightning in Loop Antenna

It seems to be a pretty straightforward question: what is the signal induced in a magnetic loop antenna by the radiation from a lightning stroke?


Obviously the answer will pop out of Faraday's Law, but to apply that we need to know:
  • the area of the loops,
  • the size of the (wave) magnetic field and
  • the rate of change of the magnetic field.
The first of these is the easiest: 58 m2.

The amplitude of the wave's magnetic field component is a little more tricky. There are some signals, like those from transmitters, which are pretty much stable in amplitude. But the majority of the noise in the Very Low Frequency (VLF) band comes from the impulsive bursts of radiation generated by lightning, known as sferics. These can also vary in amplitude depending on the intensity of the lightning and the distance from the antenna. Reference to R. K. Said, “Accurate and Efficient Long-Range Lightning Geo-Location Using a VLF Radio Atmospheric Waveform Bank,” PhD Thesis, Stanford University, 2009 gives an amplitude of around 500 pT for a sferic at night.

Finally the rate of change is related to the frequency of the wave and we can just assume that this is around 5 kHz.

So, putting that all together gives

V ~ ω A B = 2 * π * 5 kHz x 58 m2 x 500 pT ≈ 1 mV.

Which seems pretty small and is why you need a rather good preamplifier.

Wedding Table Seating

Been getting in touch with my artistic side.