The twisted trees revisited

A couple of days ago, we posted some photographs of a twisted tree that had grown with a twisted trunk and branches. Remarkably, this resulted in a lot of feedback, with multiple e-mails, corridor conversations and even a web log comment with suggestions and ideas as to the cause of this strange phenomenon.

We also now have a piece of deadwood propped up outside the door of the EISCAT building (and I've no idea who put it there!).

Where did that come from? (Photo: D. McKay-Bukowski)

And, curiously, the opinions on the cause of this vary. There have been some suggestions that it is solar loading, others that it is a wind shear effect and others that it is disease. These have been backed up with various web links and articles. For example:

• http://www.asknature.org/strategy/e70b6b7753773a7177fe8358ec26ed2c#.U4bhTCgsH7M
• http://www.science-projects.com/TreeTwist/TreeTwist.htm

Although these are not very convincing. Certainly wind effects are unlikely, given that the example we found was a one off amongst thousands of other trees that appeared quite normal.


Better was this one (på norsk  / in Norwegian):

• http://www.skogoglandskap.no/filearchive/04-2006198.pdf

We were sent a scientific reference, too

Kubler, H. Function of spiral grain in trees ; Department of Forestry, University of Wisconsin-Madison, 1630 Linden Drive, Madison, W153706, USA Received November 18, 1990/Accepted April 25, 1991
 
And this summary and link from Lassi:

"{...} The twisting in the trees is due to cell division in a “transverse direction”, i.e. it is related to tree growth. An explanation in Finnish at http://vanha.suomenluonto.fi/artikkeli-103.html {...}"

If anyone has any more information on this interesting phenomenon, please drop us an e-mail, post a comment below or let us know via Twitter.

Finnish EISCAT campaign, June 2014

A Finnish EISCAT campaign has been scheduled for June 4-10. The campaign objectives are:

1. Heatncool - D-region ionospheric heating studies by Antti K
2. Quadriphase-coded experiments - a continuation of the May 2014 campaign! Joint study by Lassi, Björn, Ilkka & Jussi. We also continue the USRP and EISCAT sampling studies, carried out also in May.
3. TomoScand verification - Ionospheric tomography reconstructions with e-POP satellite mission, joint work with Lassi (SGO) and Johannes Norberg from Finnish Meteorological Institute and a number of collaborating partners from US and Canada, who are involved in the e-POP mission.
4. EISCAT_3D receiver testing - the objective is to record EISCAT VHF long-pulse-coded experiments in Kilpisjärvi with KAIRA and new receiver technology developed by Siru, Codelma and RF-shamaanit.

Hence a multiobjective EISCAT campaign. I will travel up to Tromsø with Antti on Tuesday June 3 and head back to home around one week later. But in any case, we will try to arrive to Sodankylä prior the Midnight Sun Film Festival. A number of people will be at KAIRA site for all the campaign.

Twisted

On the walk back from Oratunturi, we came across a most unusual tree. It had been knocked down, but the odd thing was the tree itself, which appeared totally twisted. We're not sure what caused this... lightning? growth anomaly? But there were no other tree like it around.

Any ideas what might have caused this?

Offline

KAIRA has been offline for the last couple of days. We had a set of outages over the weekend that had left the station without RF signal. Power-cycling and resets had recovered the computer system, but the digital signal processing electronics remained down and we were only getting zeroes from the channels. In short, we needed to switch off until we could get this sorted.

With volunteer, hour-of-hours help from some of the ASTRON engineers, we've managed to get the system back up and running again. Turns out there were some problems with the rubidium clock but this has now been resolved.

However, during the process we discovered there was an incorrect calibration file. Apparently, the software install on 9th May activated a wrong attenuation.conf file. As KAIRA has a different cable setup than other stations this needs to be specially installed. Unfortunately, this was overloooked and we have been running with an incorrect file for the past couple of weeks. Thus, data, between 09-27-May-2014 may have problems.

Oratunturi

Near Sodankylä, there is a lake Orajärvi and near that there is a rise in the landscape. A small hill, named Oratunturi lies in some forested area just to the east. It is a small drive from the Observatory and Tähtelä, and then a short walk from the roadside up along a snow-mobile track and then cross country to the hill top. It certainly makes for a nice afternoon out... assuming the weather is okay.

Shelter on the way to the top.

The final ascent (which makes it sound a lot more dramatic than it was).

Looking back over the rock landscape with Orajärvi in the background.

The summit of Oratunturi. Pretty windy, actually.

Solar observing over the weekend

Over the weekend, KAIRA was conducting some more solar observing. We were trying out some new data acquisition modes, software and schedules. The sun was moderately active, which was good.

However, we were struck by some serious storms on the Friday night, which caused no end of problems. I suspect that things might still require attention and we will be looking into that today.

Summer sun

We are now within a month of mid-summer and the days are pretty much continuous now. The skies have been pretty grey, but they did open up yesterday to give a lovely burst of light and warmth.

Summer sun through the forest near Orajärvi. (Photo: D. McKay-Bukowski)

There's solar observing going on at KAIRA at the moment. I wonder how it's going?

Tähtelä Seminar

Yesterday, Dr. Simo Ali-Löytty from Tampere University of Technology/ Dept. of Mathematics gave a seminar talk as a base for discussion on possible joint research activities in the future.
He described the research done by his research group, Personal Positioning Algorithms Research Group at Department of Mathematics. After his talk we had a joint discussion on ionospheric effects on navigation and possible interests for joint research projects.

Simo Ali-Löytty from Tampere University of Technology (Photo: E. Turunen)

New KAIRA computer

So, we've bought a new data acquisition machine for KAIRA. Not exactly the shape one would normally expect from a computer...

A bit of sunshine

Some warm weather and bit of sunshine. We predicted the mosquitoes would follow in a few days. It actually took them 5 hours. Still the weather was pleasant enough to sit outside for afternoon coffee.

The EISCAT 32m dish in the dawn sunshine (Photo: D. McKay-Bukowski)

Further investigations on the strange solar ripple

We've been following the progress on trying to understand a strange ripple in some recent solar observations.





As each antenna has two polarisations, we plot first the X-polarisation and the Y-polarisation. They are done separately, to avoid a strong flickering effect (which is due to the different responses to the event between the two polarisations).

The "RCU" number is the Reciever Unit number. The even RCUs are for the X-polarisation and the odd ones are for the Y-polarisation. Three RCUs have been omitted (68,69, and 70) as these were offline at the time the observations were made.

Actually, we noticed that they oscillate. The oscillation is small to start with and then it increases. The movement is small, but those fringes waver with RCU number.


RCU number is a function of the antenna number.

   RCU 0,1 = LBA #L00
   RCU 2,3 = LBA #L01  
       :
       :
   RCU 94,95 = LBA #L47

And, if you look at the map of the array, and join the dots in numeric order, you get this:

So, then what I did was to look for where the minimum fringes and maximum fringes occur. In other words, as the pattern moves up and down, what are the local min/max points in that oscillation.

I noted the RCU numbers, determined the antenna numbers and plotted them. I also note the direction of the sun during this time (roughly).

This tells as that the fringe pattern is associated with distance from the sun. Well, it is not likely to be that directly, but because there is a mound with the LBAs, there will be more flat ground between #L43 and the sun than #L35. This snow/ground could be causing reflections.

What these results tell us, though, is that the original hypothesis of a reflection off the reindeer fence or gate is actually pretty unlikely.

So there are now two likes of thought. One is that this is a snow effect and some modelling is going on to investigate this.

The other is that it is an ionospheric refraction effect.

Neither idea is firm yet and investigations remain ongoing.

Snow mounds

As the snow starts to melt away, we are left with great mounds of snow. This is where the tractors and ploughs have shoved them off the roads during winter clearing operations. Of course the snow piles are quite high (sometimes as much as 3 metres) and they take a while to melt away.

Just over 2m tall. (Photo: D. McKay-Bukowski)

Snow mounds around the main carpark at Tähtelä (Photo: D. McKay-Bukowski)

Spring

Today's photo was from a couple of days ago. Spring is well and truly here now. The snow is starting to melt and there are great pools of water everywhere.

The 32m dish, reflected in rain splattered puddles. (Photo: D. McKay-Bukowski)

EIT & GMRF paper published in Inverse Problems and Imaging

Our paper on electrical impedance tomography and Gaussian Markov random field priors has been published in May issue of Inverse Problems of Imaging. You can find the paper at the IPI website http://aimsciences.org/journals/displayArticlesnew.jsp?paperID=9912. This paper was discussed in an earlier post at http://kaira.sgo.fi/2014/03/latest-results-bayesian-inversion-on.html. Below we have the reference and abstract of the paper as well as one image, where we have visualised samples of the anisotropic and inhomogeneous Gaussian Markov random fields.

The final reference is:

L. Roininen, J. M. J. Huttunen and S. Lasanen, Whittle-Matérn priors for Bayesian statistical inversion with applications in electrical impedance tomography, Inverse Problems and Imaging, 8 (2014) 561-586.

Abstract: 

We study flexible and proper smoothness priors for Bayesian statistical inverse problems by using Whittle-Matérn Gaussian random fields. We review earlier results on finite-difference approximations of certain Whittle-Matérn random field in ℝ2. Then we derive finite-element method approximations and show that the discrete approximations can be expressed as solutions of sparse stochastic matrix equations. Such equations are known to be computationally efficient and useful in inverse problems with a large number of unknowns. 

The presented construction of Whittle-Matérn correlation functions allows both isotropic or anisotropic priors with adjustable parameters in correlation length and variance. These parameters can be used, for example, to model spatially varying structural information of unknowns. 

As numerical examples, we apply the developed priors to two-dimensional electrical impedance tomography problems.

New version of GNU Ionospheric Tomography Receiver Out!

I finally got around to updating the ionospheric tomography receiver code than can be used to measure relative TEC using simple ground stations that listen to satellites.

Improvements are in stability, performance, phase curve fidelity, as well as in data portability. The code now uses only python and c++. The data container is now the widely supported hdf5 format. Other minor improvements include better Doppler residual estimation, as well as a new hybrid coherent and incoherent integration based phase curve estimation method that also produces error estimates for the phase curve. The performance of the new phase curve estimator is better with low signal to noise ratio.

The new algorithm is better at estimating the Doppler residuals (Doppler shift not predicted by the ephemeris), which allows me to coherently integrate longer vectors of data (use a more narrow bandwidth) and get better signal to noise ratio. This also has the effect of smearing out interference spectrally, which weakens the power spectral density overlap with the satellite. Because of this, the new algorithm produces much less jumps in the phase curve when an interfering signal intersects the satellite signal.

EISCAT_3D User Meeting 2014

The 6th EISCAT_3D User Meeting is going on in Uppsala, Sweden. We started the meeting on Monday afternoon and will finish by midday Wednesday. This meeting has been held annually in Uppsala in May. This year's special topic is complementary measurements.

More info about the event at http://www.space.irfu.se/workshops/EISCAT-3D_User2014/ and the presentations slides at https://www.eiscat3d.se/content/6th-eiscat3d-user-meeting-uppsala-12-14-may-2014.  Here we feature couple photos from the meeting and Uppsala!

The meeting takes place in the Ångströmslaboratoriet of the Uppsala University!

EISCAT Director Craig Heinselman opening the meeting.

Kjellmar Oksavik talking about plasma instabilities and new receivers in Svalbard and Bjørnøya.

.... and here's a coffee break and some informal discussions.

Yep, a photo of the writer of this web log posting giving a talk!

A view from the midtown by the river.

1000 Web Log Posts

This is the 1000th post on the KAIRA web log. Thanks for reading it!

When this little project got started, it was just to keep a small number of people up-to-date with the construction and planning progress of KAIRA. However, it has grown over past couple of years and is now grown beyond what we had originally envisaged to become one of the main outreach programmes of Sodankylä Geophysical Observatory.

Now that we've reached this milestone, we're going to use the oppotrunity to look at the highlights and achievements of our web log. (Oh, and I should note that the use of the word "milestone" for the 1000th post is quite apt. A Roman Mile is defined as 1000 double-paces; one step with each foot).

So, here are the highlights of the last 1000...

The historic

Ultimately, the KAIRA web log has been chronicling the history of the KAIRA project, from the first ideas and tentative steps to the major events and significant accomplishments. There have been a few posts along the way that fall into this category. But these few strike us as being the critical ones.

Post #1 -- The very first post of our web log. Wow! That seems like an eternity ago.

HBA array complete -- when we installed the last High-Band Anntenna (HBA) tile at KAIRA.

LBA array complete -- when we finished the build of the KAIRA Low-Band Antenna (LBA) array.

KAIRA official opening -- The day we officially opened the KAIRA facility.

Achievements -- For the important steps KAIRA has made scientifically, we've a page with the highlights.

... and of course the one you're reading right now!

The series

KAIRA (Kilpisjärvi Atmospheric Imaging Receiver Array) is a radio receiver system. It can measure very faint radio signals and determine very precisely which directions those signals are coming from. It uses LOFAR antennas and signal processing to accomplish this. If you ignore the details of how the data are processed and interpreted, you can safely say that antennas of LOFAR and KAIRA are doing the same sort of thing.
On occasion, we've run a series on something. Although individual posts themselves are not so dramatic, the collective sum of the parts has proven significant. Some examples include:

How does KAIRA work -- A series explaining how a phased array works. Became the basis of the hugely successful "Digital Static" radio telescope lecture.

Blizzard 2014! -- The account of the storm damage from the blizzard on the 8th March 2014.

Destructive Test -- The environmental testing of LFOAR hardware in the Arctic, leading to the destroying of an HBA tile under snow loading.

Progress reports -- During the build we kept the team back at SGO, and in the wider scientific community, up-to-date with the progress that was being made daily on the installation of KAIRA.

The popular

We have been surprised the popularity of the KAIRA web log. From very humble beginnings, we now have more than 10,000 page hits per month... which is not bad for a small, highly-specialised scientific experiment run by a very small team. Yet popular it is. And although some of our more popular posts are from KAIRA, there are actually quite a few that are not. They just happened to be by KAIRA staff about local or technical things. Here are some of the top ones:

The KAIRA film -- A short documentary about KAIRA and what is for. The film was shown at the official opening, and made fully public at the LOFAR 2014 science meeting.

Passive Radar with $16 dual coherent channel rtlsdr dongle receiver -- This was the top post from a hugely popular series put up by Juha on his work on passive radar. With some cheap off-the-shelf hardware, Juha demonstrated the most amazing series of passive radar applications.

Are 2012 DA14 and the Chelyabinsk meteor related? -- The meteor was a current event that caught us unawares, but we happened to be observing DA2014 at the time and were able to make the first breakthrough in determining critical parameters about the event.

Lemmings -- This post had a series of photographs by Stuart Keenan (who was on the HBA installation team). Stuart documented a lot of the wildlife in the Kilpisjärvi area, but his stunning photographs of the lemmings was by far the most popular.

The people

Of course, we are indebted to all the authors, photographers and contributors to this web log. Photography, articles and videos from Mikko Orispää, Stuart Keenan, Joona Keskalo, Arttu Jutila, Markku Postila, Toivo Iinatti, Thomas Ulich, Esa Turunen, Brian McClave, Poppy Martin, Richard Fallows, Ilkka Virtanen, and a host of others. The editors/principle authors are Juha Vierinen, Lassi Roininen... plus a few from me.



So, thanks again for reading. We hope you've enjoyed the stories and the anecdotes and have had fun sharing a part of our scientific life, north of the Arctic circle whether under the eerie glow of the aurorae or the kind rays of the midnight sun (or, more likely, the snow and rain and more snow and sleet and more snow and gales, and snow and leaden skies).

The KAIRA HBA array (January 2013). Photo: M. Postila.

Here's to the next 1000 posts!

KAIRA Status Map

We have a new status map showing the situation with KAIRA.

This shows the actual current status:

This is available from the Status page, which can be found in the title bar of this web log.

The map shows the array layout of the antennas. The High-Band Antenna (HBA) tiles are in the top left and the Low-Band Antenna (LBA) aerials are in the lower right.   The layout is to scale, which is shown, and the direction to the VHF transmitter at Tromsø, is also indicated.

The antennas are numbered and they are also colour coded to show the Receiver Unit (RCU) mode. KAIRA has 96 RCUs and the RCU mode indicates which combination of antenna plus band-pass filter is used for the processing. Sometimes the entire array is configured to a single RCU mode and at other times it is mixed with several different modes for different antennas.

If an antenna is enabled, then the colour is bright, but if it is switched off, then it is dulled down.

In the case of a plain grey antenna icon, this means the antenna is shut down, either for maintenance, or as a result of damage.

Sometimes an antenna might be shaded with two colours like a two-tone maritime-Z-pennant. This is because each antenna has two polarisations, and there will be occasions when the RCU number/status for each polarisation is not the same.

In the bottom left, there is the legend and in the top right is the status label and the current RF-container parameters.

The image at the start of this post is "live". If you update the page, you might see ti change, depending on what KAIRA is doing. But to give an indication of what the status map might look like, here are some other static examples:

A "357"-mode solar observation. The grey antennas
are those knocked out by the March 2014 blizzard.

A mode-3 riometry observation. Storm-damaged antennas
are also present in this particular example.

Kiintojää

A couple of evenings ago, there was a very moody sunset over the Kitinen river near Sodankylä Geophysical Observatory. Along the shore, there is still fast-ice, but the mainstream is pretty clear now.

Fast ice along the Kitinen River (Photo: D. McKay-Bukowski)

The road to Tähtelä

Just to give everyone an idea of snow conditions at the main institute at Tähtelä these days, today's photograph shows the main road just before the turn-off.

Just shy of the turning to SGO. (Photo: D. McKay-Bukowski)

Yes, there is still plenty of snow around but it is melting quickly. Sodankylä Geophysical Observatory is much further south than the KAIRA site, so the conditions here are a lot clearer... unlike the snowy landscape that we saw in Lassi's photographs from the week just gone.

5 MHz EISCAT sampling ... First time ever

During the last day of the quadriphase-coded experiments, we decided to push the limits of the EISCAT sampling system by sampling at 5 MHz with one channel! This allows us to study the plasma lines. In pulse-compression quadriphase code groups are used!

This posting concludes reporting from this successful campaign! We will be back in this business early June!

Two quadriphase codes transmitted and sampled at 5 MHz at EISCAT!

Day 3: Plasma lines and preparations for June campaign

It's the last day of the quadriphase-coded EISCAT experiments. Today we will run some plasma line studies. In addition, we prepare for the upcoming TomoScand campaign (8-10 June), where our objective is to verify TomoScand ionospheric tomography reconstruction against EISCAT measurements. Below is a figure of one of the projected CASSIOPE satellite trajectories. Hence, today we study, if we can use quadriphase-coded experiments in a tracking campaign!

We will commence the operations at 10:30 UT!

... and today after the experiments, I will drive back to Sodankylä (ETA midnight)! ... and on Sunday evening I will fly to Uppsala to the EISCAT_3D User Meeting 2014 !!

EISCAT plasma parameter plot 8 May 2014

Today we continued the quadriphase-coded experiments with EISCAT UHF in Tromsø, Norway! For comparison purposes, we ran first regular Beata experiment 11:00-11:12 UT. Then we used pretty much the same setting as yesterday, i.e. four code cycles. Below are the preliminary plasma parameter fits. We note that the F-region maximum is in rather good correspondence with the dynasonde measurement! We had one crowbar at 12:26!

Day 2: Quadriphase-coded expms continue

Today we will run nearly the same experiment as yesterday. We have slightly modified the quadriphase codes and this naturally affects analysis. We will report the results in Twitter and hopefully also in the blog in the afternoon! Operations commence at 11:00 UT !!!

In addition to the EISCAT UHF and VHF radars, there is a significant number of other instruments at the EISCAT site. From the KAIRA point of view, one of the most interesting instruments is the MORRO 56 MHz MST radar. The MORRO signals can be received with the KAIRA LBA field! Hence, below is a photo of the MORRO antenna field! ... and yes it is again a very beautiful day in Tromsø!!

First quadriphase-coded experiment in EISCAT's history

We report that we have successfully carried out a quadriphase-coded incoherent scatter radar experiment with EISCAT UHF in Tromsø, Norway! Today's objective was simple: Transmit quadriphase-coded waveforms and see that the results are somewhat similar to regular binary-coded Beata experiment. Below we have transmitted waveforms of the experiments and ACF images of the binary-coded and quadriphase coded experiments.

Hence, we proudly conclude that EISCAT UHF is upgraded to quadriphase-coding!

Transmitted waveforms of the binary-coded and quadriphase-coded experiments.

ACF of the binary-coded Beata experiment.

ACF of the quadriphase-coded experiment.

Day 1: Quadriphase-coded experiments

It's the first day of the quadriphase-code experiments at EISCAT Tromsø! This is a joint Finnish-Norwegian campaign, with a little help from Millstone Hill. We have three basic code cycles:

ac32bin    is the 32-bit binary alternating code from EISCAT UHF beata (64 codes)

cg32bin    is an optimised cycle of 32-bit binary codes (16 codes)

cg32quad is an optimised cycle of 64-bit quadriphase codes (16 codes)

In addition we have an "extra" codeset, a normal beata modulation (ac32bin), but implemented using the 4-phase shifter HW which otherwise is used in the 4-phase code set.

So let us hope that everything goes smoothly!

Panorama of the EISCAT transmitter site: Left-hand side is the VHF radar and right-hand side is the UHF radar! We will use the UHF for this experiment!

Route EISCAT Sodankylä - EISCAT Tromsø

The journey from Sodankylä Observatory to the EISCAT transmitter site in Norway is around 510 kilometres. The journey typically takes around 7 hours, but during bad winter storms, it can be around 10-11 hours. Yesterday, during the travel from Sodankylä up to Tromsø, the weather was excellent. Below is a set of photos taken in various places along this scenic route!

Starting point: Sodankylä 32-metre EISCAT receiver dish

Levi mountain in Kittilä

View to Pallas

Arriving to Kaaresuvanto

Mountain Lammastunturi and the Passat "SLZ"

View to south around 35 km south of Kilpisjärvi

Panorama of Lake Kilpisjärvi

Saana mountain and local store

Between Kilpisjärvi and Skibotn, there is major road construction! Maximum waiting time around 30 minutes!

Fjord-view in Skibotn

Driving on the seaside

Finally arrived, this is the EISCAT UHF transmitter site!

... and here is the VHF radar!