Halos on the night of 14/15 December 2016 in Rovaniemi, part III

Opposite to the lamp I could see something that thus far has appeared for me only in simulations: diffuse arcs extending all the way from the anthelic point to the subanthelic point. The effect is not that impressive in photos. Neither is the anthelion which really caught my attention: an anthelion formed against the ground in just few meters of air space. In the image above I had tilted the camera sideways so that it is not aligned with the central column of the tripod. This makes the shadow in the middle of the arcs less disturbing. In the image below, taken earlier, I had not yet done this move and there is a more prominent shadow. The image above is a bit spoiled because of spotlight light getting in from the viewfinder. I thought the camera was broken and bought a new one two days later... On one night in the beginning of January Mikkilä called while I was out photographing at around -35° C (-31° F) temps, and he told it was about light leaking. I didn't buy it, having a false memory of the effect appearing also when I shot towards the lamp. In the end it had to dawn that Mikkilä was right and also a feeling (maybe false too) that I must have known this thing in the past but my brain had buried it too deep by now.

So, where was I... yes, of some interest in these photos is the blue edge of the diffuse arc (the 3157 type).

Below are two more shots showing the anomalous Hastgener. These stages of the display are not really that poor (see part II), was I too hasty to make that connection? (Somehow I succeeded in not seeing these photos when writing the part II even if they were ready made in the same folder). Notice the left side subparhelion which seems tilted in the first image which is a single frame. The breeze makes localized, passing disturbances in crystals' orientation and can cause effects like this. At least that's what I seem to think now, but who knows if it is true. Anyway, I think there is a frame from stacking series from one other display where the other subparhelion is completely missing.

Halos on the night of 14/15 December 2016 in Rovaniemi, part II

Here is a collection of images showing an arc that looks like a downwards curving Hastings or Wegener. It's nothing new: the arc was first observed in Rovaniemi on 23 November 2015 and again nine days later in the evening of 2 December. I don't know how it is made, but it seems to occur when the display is suboptimal as compared to its best development. A halo that thrives on (relatively) crappy crystals?

In the display on the evening of 14 December 2016 this anomalous Hastgener was captured on several stacks, one of which is shown above and which also has normal Hastgener. Below are two more photos of which at least the left side one shows the effect. It was true to form, as these stages did not represent the peak of the display.

There was an additional oddity: the Hastgener / anomalous Hastgener has a kind of parhelia near the tangent arc. The feature occurred intermittently and was well visible to the eye. Below are two images showing this "parhelia", the one on the left is a single frame. The brightening seems to be also present in the main image above.

Finnish Display 2nd September 2017

Kimmo Laitinen captured a nice display with Wegener arcs and a really strong lower tangent arc on the 2nd September 2017. I'll let Kimmo describe his observation in greater detail in his own words. 

He says, "we drove from Siilinjarvi to our summer house in Leppavirta via Kuopio. In Siilinjarvi the weather was sunny but before Kuopio a thin uniform layer of high clouds covered the sun and we spotted the first halos as we passed the city centre of Kuopio about 11.45.... At this point the 22 deg lower tangent arc was not so impressive and only a short section of the parhelic circle could be seen. Then we went on southward to the Puutossalmi cable ferry.... In Puutossalmi the 22 deg lower tangent arc was the most impressive and reflected nicely from the lake. After the ferry the 22 deg lower tangent arc disappeared but the parhelic circle became all the time longer and a very faint Wegener arc was seen by the naked eye. After driving a few km more southward the low clouds disappeared from the northern sky and the parhelic circle became complete about 12.30 in the village of Lansi-Saamainen in Leppävirta. The 120 deg parhelia were clearly visible and the intersection of the Wegener arcs with the parhelic circle was revealed from the images. After this the display got dimmer but still lasted for a few hours.

All images used by permission. © Kimmo Laitinen. 

The taxonomy of halos - towards a new system of halo classification and nomenclature

The comments in a recent post brought very sharply into focus the problem of halo classification and nomenclature; what do we call a particular halo form, why do we call it that, who gets to decide on that name and where does it fit into the overall halo classification.

The study of halos is, generally speaking, a relatively new science and discipline. Serious research into halos has accelerated during the latter half of the twentieth century up to the present and by and large it has been overwhelmingly led by committed amateurs with only the occasional dalliance of “professionals”. One result of this has been a certain lack of clarity in the classification and naming of halos. We can all probably think of at least one halo that has two or more names or halos that have had a change of name over the years as the understanding of its nature has deepened.

In other branches of science there are various organisations and protocols which govern the naming and ordering of things. However, in the halo community we are basically on our own. No-one is going to step in and wave a magic wand and it is up to us as a community to come to some sort of consensus and develop a meaningful and workable taxonomy.

In recent years we have sometimes witnessed very heated debates amongst those who are most active in serious halo research. This has led to a situation where because of a certain amount of stubbornness and entrenched views, individuals and the wider community are no longer addressing and engaging with the problem. The aim of this short post is therefore to try to open up the conversation once more and solicit new ideas and suggestions on how we should proceed. The need for this discussion is becoming increasingly urgent. There are so many new halos being discovered all the time that we need some way of describing them and being able to relate them to some overarching system of classification.

What I would like you to do is to think about taxonomy in general, and halo classification and nomenclature in particular. It may be that no one system is “correct” and that two or more may adequately describe and account for what we see. I think that whatever system is finally decided upon it should be fairly open and flexible, so that it is able to handle the new and the unexpected.

I appreciate that this may seem to be a very dry subject when many people these days are content to see endless photos of increasingly rare and spectacular displays. However, I think it is of the utmost importance to our discipline. We need to get it right now so as to prevent serious problems in the future.

Over to you, the comments are open!

Halos on the night of 14/15 December 2016 in Rovaniemi, part I

Last mid-December, Rovaniemi was shrouded in fog for five days in a row. With temperatures hovering in -5 to -10 C range, the conditions were as good as one can hope for. Just add icy nuclei from snow guns in the air and fog is guaranteed to freeze into a violent display.

The five day diamond dust feast did not materialize. The guns were shut down after a couple of hours after the dark of the second night, and then it was just fog. But I was there on those two first nights to take photos, a selection of which I am going to show in this and coming posts.

I start by two photos from the first night of 14/15 December. Both have, inside the Tricker arc, a faint colored arc, best visible in the blue-minus-red versions. Upon first becoming aware of this feature, I thought, with some excitement, that it might be an exotic halo. This state of mind did not last long, however, because soon the arc turned up in a simulation.

The halo is born from raypaths 3162 and 3152 in column oriented crystals. By its appearance it is a vertically mirrored copy of the more commonly photographed 361/351 arc, which is also seen in the photo (and which has been treated in an article by Walt Tape). At the upper right of the above image is simulation where these arcs are marked, respectively, by left and right pointing arrows. Two column oriented populations were used. The 3152/3162 arc is made by the population that rotates 20 degrees, not by the fully rotating population (see parameter table below). At the lower right of the above image is another simulation, where the the 3152/3162 arc from the limited rotation population is shown without other halos.

Blue subsun finally about right

closeup of the photo below

The year is gearing towards winter, the first glitter in northern Finland expected in less than two months. While waiting for that, I think I should continue clearing the backlog of last winter's results from Rovaniemi before new stuff starts piling up on top and risking buried-in-drawer fate. There is still plenty to show – even what might be called as major displays.

To not inflate it right away, lets start with a more moderate, but nevertheless interesting display. On the night of 16/17 January 2017 a display with full set of kaleidoscopic arcs appeared, and towards the end of the action, when it turned plate dominated, I tried to get the blue subsun photographed.

Earlier past winter and the one before, on a couple of attempts at blue subsun that I had myself or with friends, the aim was to get the lamp elevation right so that the blue would be exactly at the center of the subsun (otherwise you might feel a tinge of uncomfort calling it a blue subsun). It is a precision job: the optimum is at right about 58.5 degree light source elevation, with the tolerance of around half a degree, after which you may not be able to sell it to a demanding customer.

We did't get it quite right then, or the display was otherwise uninspiring, but this time there is a clear blue color passing pretty much through a middle of a well defined subsun. Connoisseurs might still see manoeuvre for one or two tenth of degree improvement, but I am good enough with this to not pay effort to go after it no more. However, there is some other stuff that warrants visiting the extremely low lamp haloversum (like sub-cha and its extension), so blue subsuns are certainly going to come along with the ride.

Halos from deep space

Now don't get too excited, it's not the news of first exoplanet halo observation. Instead, a space craft has observed halos on Earth - from deep space, 1,5 million kilometers from Earth.
 
NOAA’s Deep Space Climate Observatory, (DSCOVR) is located at first Lagrangian point. It's 1,5 million km from Earth, between Earth and the Sun. It takes hourly (or every two hours, depending on time of year) a picture of sunlit Earth with its Earth Polychromatic Imaging Camera (EPIC). Some of these pictures show a bright glint, which was initially thought to be solar reflection from still ocean surface but soon discovered appearing on land areas too. Size of the glint was too big to be caused by lakes. An idea of horizontally oriented ice crystals in upper atmosphere as a reflecting surface was introduced and challenged with series of tests. It proved to be a winning theory. One of the tests was to study whether the angle between the Sun and Earth is the same as the angle between the spacecraft and Earth on the location of the glint. And it was a match for every glint recorded. So, the reflection from ice crystals can be regarded as a halo, namely a subsun. With a very maximum Sun elevation.

One might think that 1,5 million kilometers is a record breaking distance to observe halo's, but while investigating the glints NASA scientists found out that similar glints were noticed in pictures taken by Galileo spacecraft back in 1993, when it was on its way to study Jupiter and its moons. Galileo took the pictures at 2,08 million km distance from Earth. Originally glints recorded by Galileo were reported to be seen only over oceans, not over land, but that was a mistake. When inspected again, Galileo footage clearly shows glints also over land areas.

Not only being a curiosity for halo enthusiasts, detecting similar glints could be used to study exoplanets. If exo can produce halos it could be a sign of water in its atmosphere and that can give a hint about planets habitability. Hubble Space telescope successor, James Webb Space Telescope (JWST) is planned to be launched in October 2018. It will be stationed at second Lagrangian point, so observing subsun on Earth is impossible for JWST, but maybe it is capable of spotting extra Terrestrial halos? Or maybe we need to wait for the next generation telescope for that. But perhaps, some day this articles header can be re-used, having a slightly more exciting meaning.


The original article from American Geophysical Union (AGU): Ice particles in Earth’s atmosphere create bright flashes seen from space