Science Post: Riometers, Photometers, Magnetometers, and SuperDARN

The broadband riometer array at Arrival Heights

So, last time I said that I'd start talking about some of the science I look after here at McMurdo. A-111 is a combined project involving, a riometer array, photometers, and a magnetometer. The riometer and photometer systems help study the process of energy transfer from the solar winds to the Earth's magnetosphere and ionosphere at high magnetic latitudes. The riometer array picks up galactic radio noise, which is assumed to be constant at any point in the celestial sphere. These radio signals are absorbed by ionized air, so fluctuations in signal intensity signal changes in the ionization level. These changes can be cause by solar UV and EUV radiation, galactic cosmic rays, solar flare protons, or aurora-associated energetic electrons. The data is process to isolate effects due to energetic particles. The photometers measure photo-emissions at two auroral wavelengths for correlation with the riometer data. Lastly, the magnetometer is used to study hydromagnetic wave phenomena in the magnetosphere. So, all of this is a long way of saying that this project studies aurora.

Checking the signal cables out to the riometer array

My responsibilities for this project include daily and monthly checks on equipment. Every day I check on the computer read-outs, to make sure that data is still being collected and transmitted off continent. Earlier this season, one of the computers failed which made for an exciting couple of weeks. However, Gil and Bob, two of the grantees on the project came down last week, bringing with them a replacement computer, and a brand new one. The new one is going to run in parallel with the other computers in the system, and if all goes well, it will completely replace the others next year when the group comes back. At the beginning of each month I also do a walking inspection of the signal cables and the riometer array up at Arrival Heights. And since I am "off station" I get to bring a buddy, or buddies, with me for safety and extra hands and eyes. We check the cables for wear, patching them with electrical tape if need be,  and check the riometer array for alignment, missing antenna arms, and damaged anchor/stabilization lines. It is a nice hike in good weather, and makes me pretty popular with people who want to get off station for a couple of hours.

The imaging riometer antenna.

One of the other projects I support is the Super Dual Auroral Radar Network, or SuperDARN for short. The McMurdo SuperDARN is part of a network of 32  radar systems looking into the polar regions of the Earth. The radars measure the position and velocity of plasma irregularities in Earth's ionosphere. The movement of these irregularities responds to energy coupled into the auroral regions from the solar wind and magnetosphere. This means that SuperDARN provides information regarding the Earth's interaction with the space environment.

In the SuperDARN antenna field

Every week I do a drive by of the antenna field, checking to see that the antennae are still standing and that the anchor lines are still attached. If we ever get big storms, I'll walk the field to do a closer inspection, which I did at the end of last month, when we had our one Condition 2 day so far this summer. Everything was still in good shape.

Melt pools, now with actual liquid

 Outside of science a lot has been happening. We celebrated Thanksgiving almost a week early, at the the food was great. We also got a two day weekend for the occasion, which is always exciting. There were a number of activities to over the weekend, including a Turkey Trot 5K out to Scott Base and back. That included an uphill almost the entire first half and 15 knot winds blowing in the wrong direction on the way out, and in sort of the right direction for the way back in. The weather has gotten really nice. We hit 35F earlier this week, which isn't unusual for this time of year, but temperatures in the 20s are more normal. With the warmer temperatures, we've also officially entered mud season. The roads are kind of a mess in places, and we have little rivers running all over the place. On my last pressure ridge trip, we saw four seals, three of them up close.

A pregnant seal right off the flag line.

One day last week, after finishing up soccer, we came outside to be treated to a pretty impressive display of fata morgana, which is a type of superior mirage.

Fata morgana across the Sound.

From what I've heard, this phenomenon cause a lot of trouble to the early explorers of Antarctica. They would come outside one day to see these huge cliffs across the way, and decide they wanted nothing to do with that. Then they'd come back a while later and the cliffs would be gone. The name itself is derived from the Latin for fairy and from Morgan le Fey, the sorceress from Arthurian legend. It's pretty cool.
And I got a package from home, which is always very exciting.

The View From Arrival Heights, Warm Weather, and other Miscellanea

A selfie up at Arrival Heights. On a clear day, you'd be able to see Mt. Erebus behind 2nd Crater.

 So, McMurdo  has changed a lot since I got here a month and a half ago. We are now at about 900 people, which is about as big as it’ll get. We still have more people coming in, but field camps are opening up, so a lot of the science groups will be heading out as soon as the helo’s are available.
I’m still waiting to find out if I’ll be getting a roommate. Since there are a bunch of people no longer coming down due to the shut-down and start-up, there is room in the upper-case dorm (like the one I’m in) and the administration has opened those dorms up to folks with fewer ice days (It is going from 131 days on ice, down to 127 days). The upper case dorms have bigger rooms, with a bathroom shared between 4 people, rather than a floor of people. I know a couple of people who were notified that they could move if they wanted to. They decided not to, since they are settled in to their room and they’ve actually got a great view, and the dorm they are in is empty enough that they actually have the bathroom to themselves, at least for now. So, it is possible that other people will feel the same way, and I’ll be able to procrastinate moving my stuff to one side of my room for a while longer.

I posted a couple of pictures on Facebook of my Halloween costume, but I thought I put a few up here for those that didn’t see them. I went as Tony Stark, which meant I could dress the way I normally do, and just added a home-made “arc reactor”, which consisted of recycled LEDs and computer part.

A work in progress. This is before I mounted the cover on it.

Finished product. I mounted the whole thing on the chest strap for my HR monitor, and stuck the battery in my pocket.

The weather has gotten a lot warmer in the last week. Warm in this case means that it has been in the teens and low twenties. And the wind has been low, too. All this means is that I’ve been able to stop wearing my big jacket, and have been running around in my Vakava jacket, or a sweatshirt, and maybe, maybe a hat. The warm weather has also started one of three McMurdo seasons: the slush/mud season. There have been ankle deep puddles popping up all over the place, especially around high traffic areas, which can make getting to meals a challenge. From what I hear, it will only get worse, up to some building requiring that you take your boots off before coming inside. Once the mud season ends, which is when the temperature starts to drop again and things freeze, we get dust season. Then sometime around last sunset we’ll get into cold/snow season, which will last throughout the austral winter and into winfly next spring.

Mt. Erebus from Arrival Heights. There is a little orthographic uplift happening, which is what causes the layers of clouds.

I think that I’ve said it before, but Arrival Heights, where a bunch of my projects live, has probably one of the best views of Erebus and McMurdo Sound on station. And I’ve got pictures to prove it. I keep meaning to bring my wide-angle lens up to take in the full view from the roof, but that hasn’t happened yet. I will post that when I finally get around to taking it.

Looking out towards McMurdo Sound

Along with the instruments in the Arrival Heights building, I’ve also got antennae out away from the building, and up in Second Crater (about a 1mi hike from Arrival Heights). About once a month I hike out to these, to check cables, realign antenna and just see what kind of shape things are in. Since it is technically away from station, I am supposed to bring a buddy along, for safety. So, at the beginning of the month Erin and Debb joined me to do just that.

Mt. Erebus from 2nd Crater

Erin and Debb checking out one of the anchors for the VLF antenna

Erin with the Royal Society Range in the background

Next time I’ll start talking about some of the different projects I’m working on. And I will leave you with this, the terror of McMurdo:

The Skua, a scourge upon those who carry their food outdoors.

Pressure Ridges

The pressure ridges with Castle Rock and Mt. Erebus in the background

I was able to get out to the pressure ridges during my first two weeks in McMurdo. I liked them so much that when the Rec department started looking for volunteers to lead pressure ridge tours, I signed up right away. Alister, the guide from my first tour, also ran the training for the volunteer guides. There were 11 of us in my class, and another 10 who got trained in later. We started with about an hour in the classroom, about the pressure ridges and some of the dangers we should be in the look out for when we take groups out.

The parking meter for Americans at Scott Base

So, what are the pressure ridges? In a lot of ways they are very similar to the mountain ranges that are created when plate tectonics shift. They are formed when the ice shelf (glacial ice, in this case the McMurdo Ice Shelf) collides with the sea ice that forms along the shore. The glacial ice begins to crush the much thinner sea ice, which causes ripples and waves to form in the ice.

A crude drawing of the pressure ridges. 

Eventually these waves buckle and crack. If the waves crack on the top portion, or crest, then entire slabs of ice can rise from the surface.

Some interesting ripples on the underside of an ice slab

If the bottom portion, or trough, cracks, it forms a “melt pool”. Melt pool is a misnomer, since, at least at this point in the season, nothing is melting; it’s just sea water flowing through the crack in the ice to form a pool.

Melt pool surrounded by ridges

And another view

Many times, the Wendell seals, who live on fast ice (as opposed to the Crab Eaters and Leopard seals, who live out in the pack ice) will use the cracks as breath holes, rather than having to make their own with their teeth. Seems like a good plan to me. Once a male seal takes over one of these holes, they will defend it from other males, since who ever controls the hole, controls the females in the area. Right now the seals are in pupping season, so in another month or two we should have seal pups hanging out on the ice.