Turned cloudy today, rained last night but stayed fine today. Some promising breaks in the cloud hint at sunny weather later. No radar for me today but exciting ground breaking UK experiments are currently underway. The heating facility is being used to probe the lower ionosphere using partial reflection. Magnetospheric radar, mesospheric radar, ionospheric heating - is there anything that field of antennas cannot do?
My radar run yesterday was not so hot. Things were very quiet and all I really got was a nice quiet, solar illuminated ionosphere. Nothing to help me with my work but a couple of cool things showed up in the data anyway. The plot to the right shows the estimated electron density provided by the VHF radar.
You can see how the electron concentration is highest at about 200 km (F-layer) and decreases with descending altitude until it disappears below ~90 km (D-layer); the radar is just not sensitive enough to pick out the much lower electron density below there.
If you look closely from ~12:45 UT you can see an undulation in the data, noticeable in the bit coloured green. This looks like gravity waves to me (not to be confused with gravitational waves), which are generated in the troposphere and are important for transferring energy and momentum to the mesosphere. Caused by airflow over mountains or weather fronts, these disturbances are called gravity waves since gravity acts as the restoring force that causes the oscillation.
Another interesting feature is the appearance of PMSE layers - polar mesosphere summer echoes). The most obvious is around 14:00 UT where there are strong radar echoes. These are not true estimates of the electron density, rather they are caused by coherent scatter where more power is returned to the radar giving the false impression of much higher electron density. The coherent scatter is actually from irregularities with spacing of half the radar wavelength (in this case about 70cm). PMSE are caused by the presence of electrically charged ice particles - the mesopause is very cold so water vapour freezes. These same ice particles cause noctilucent clouds.
So there may be something useful in that data even if not for me.
Wednesday, July 29, 2009
Tuesday, July 28, 2009
I was wondering about this on Sunday night.
Schumacher would consider return
Michael Schumacher is not ruling out the possibility of standing in for injured Ferrari driver Felipe Massa.
In actuality I think it unlikely that he will return to stand in for Massa. At the risk of sounding somewhat mercenary Ferrari would be better off trying out someone new (to them at least). They have to think to the future and at the moment that might not include having Massa in a car again.
Posted by Kav at 15:44
Well, its campaign time and here I am sat in the north of Norway. Except rather than snow, ice and rain I can see sunshine and mountains of green. It makes a refreshing change.
I arrived yesterday evening into lovely sunshine and warm temperatures, somewhat removed from the cold and snow into which I normally arrive.
The drive from the airport to the radar site was very picturesque and I did not have to worry about icy roads and so could relax and enjoy it.
It was almost enough to wipe away the pains of a 6am start followed by a three leg journey incorporating a high speed dash through Oslo airport to make my final connection. I was pleasantly surprised to find my luggage on the conveyor when I arrived.
I was even more pleasantly surprised to be fed reindeer when I got to the site. Good times.
This is the first time I have been abroad since my daughter was born and I am already missing her terribly. I just hope that we take some good measurements and get some nice results from this campaign to make up for being away from home.
That said I am not terribly hopeful.
I am not here looking for aurora this time. Instead I am looking for the signature of very high energy electrons. These relativistic electrons precipitate from the magnetosphere and deposit energy in the lower D-region (or even deeper). They can have significant effects on the chemistry of that part of the atmosphere.
The radar up here is capable of detecting the tell-tale signs of these electrons and provide a means of measuring the precipitation spectrum (that is the number flux and energy of the elctrons). This is not so easy to measure in space since you want to only sample the portion of the electron population that is going into the atmosphere plus you have the difficulty of a satellite moving through the region of interest creating temporal-spatial ambiguities. From the ground we can resolve those somehwat.
One of the advantages we have over astronomers using optical telescopes is that our radars are not dependent on clear skies and we can operate happily in the daytime. However we have our own limitations; whereas chances are that astronomers can go back to the same object over and over and repeat measurements, we are working in a massively dynamic system that disallows that. No two precipitation events are identical and are highly dependent on how the magnetosphere is being driven.
The problem I have is that my timing sucks., I had hoped to catch a period of high solar wind speed, a phenomenon that enhances driving of the magnetosphere and can lead to increased relativistic electron precipitation. The image above (linking to Spaceweather.com) shows the Sun in extreme UV as seen by SOHO. What I needed was the dark spot in the upper middle (a coronal hole) to be slightly further around to the right as that would mean the solar wind burst I needed would be on its way.
I may yet get lucky for Thursday and Friday...
Posted by Kav at 13:39
Friday, July 24, 2009
Wednesday, July 22, 2009
Now I'm not normally a huge gadget person and I don't even own an iPhone but this gadget I came across today stuck me as such a brilliantly simple and elegant solution. It's called the Aircurve and it amplifies the sound from an iPhone by 10 dB WITHOUT needing electricity.
Posted by Em at 13:18