Wednesday, August 26, 2015
Monday, August 24, 2015
|Sunspot AR2403 visible at sunset today through smoke and clouds|
Posted by John Ashley at 10:41 PM
|An osprey flies away with fish in tow through smokey, western Montana skies.|
Thursday, August 20, 2015
|Sunspot AR 2403 visible through a smokey sunset on August 20th|
We have a lovely sunspot (AR 2403) spinning nicely into view over the next several days. And all of the smoke over western Montana is actually making it a lot easier to see this dark region on a dimmed-down sun.
Our roiling sun is stratified into several layers. The photosphere is a thin, outer layer that's about 60 miles (100 km) thick where the sun's energy is released as light, and this is where sunspots occur. Sunspots are actually quite bright, but they appear dark compared to the boiling plasma surrounding them. At 3,800K degrees, sunspots are about 1,500K degrees cooler than the brighter plasma. Sunspots include two groups or clusters. One group has a negative charge while the other group is positive. The darkest part of a spot is where the magnetic field is strongest.
These spots are caused by interactions in the sun's magnetic field, but we still don't fully understand the process. Smaller spots last a few days while the larger ones can persist for months and many revolutions around the sun. Because the sun isn't solid, different regions rotate at different speeds. A point on the sun's equator makes a complete revolution in about 24 Earth days, while the polar regions spin slower and take about 30 Earth days. Sunspots are concentrated in two bands on either side of the solar equator, so a big group might circle the sun in 25 days or so.
Sunspots come and go, but their numbers aren't random. They wax and wane in 11-year cycles known as solar minimum and maximum. The most recent solar minimum occurred in 2008, so we should be slowly building towards a solar maximum in 2019. Maybe by then all of this smoke will have cleared.
Posted by John Ashley at 9:43 PM
Wednesday, August 19, 2015
|Our reddish moon tonight was caused by smoke particles|
scattering away the blue wavelengths.
With a month or so to go in our fire season, Montana is a little bit over the 10-year average for number of fires (1,861 to 1,648). But acreage-wise, we've only burned about one-third of our 10-year average (118,154 to 338,252), so far.
What happens next? With all due respect to the "fighters" and the millions of dollars spent and the prayers sent skyward, it depends entirely on the weather. An early snow and our fire season ends. A late summer and we're smoked.
One hundred and five years ago today, a cold front swept across the Northern Rockies. Hurricane-force winds fanned 1,736 small fires into one or two conflagrations that burned an estimated 3,107,819 acres in Montana and Northern Idaho in just two days -- the Great Fire of 1910. That one burned 265 times the acreage of our current year-to-date total in Montana. Two hundred and sixty-five times more. And that's the year when we became obsessed with pretending to control wildfires.
Pray all you want, spend all you can, and risk thousands of young lives. But the forests will still burn. Always have. It's frustrating, I know, because we like to thump our chest and think that we're above nature. We're not. Fire season in Montana is an annual reminder of the lesson we never seem to learn.
Tuesday, August 18, 2015
Our northern flying squirrel (Glaucomys sabrinus) is built to work the night shift. Our daytime red squirrel (Tamiasciurus hudsonicus) returns to its nest before dusk because it can't see in dim light. But even though the flying squirrel is considerably smaller than its daytime cousin, its eyes are twice as large to gather more light at night. While red squirrel eyes have mostly color-detecting cone cells, flying squirrel eyes have mostly dim light-detecting rod cells.
Like other nocturnal animals, flying squirrels also have "mirror" behind their retinas that reflects dim light back to the rod cells, effectively amplifying their night vision. This tapetum layaccounts for some of the animal eyes that you and I see when we shine a flashlight into the dark -- our light reflects off the animal's tapetum bright enough for our eyes to see.
Thursday, August 13, 2015
Saturday, August 8, 2015
|Glacier National Park star party at Logan Pass, August 2015|
Saturday, July 25, 2015
She's our largest native ladybug, featuring 18 or so black spots surrounded by beige rings. These spots are set against a background color that darkens with time, starting out yellowish and turning reddish-brown as she ages.
American eyespot lady beetles range across an east-west swath of North America from Alaska to Maine, dipping down across most of Montana.
Saturday, July 18, 2015
A 9% crescent moon and an 18% crescent Venus set together at dusk, as seen from western Montana. If you were in just the right spot on this same evening in the South Pacific, the moon would see the moon pass in front of, or occult the planet Venus.