Archive for the ‘NatureShare’ Category

Species Spotlight: Luna Moth


Sunday, July 21st, 2013

Species Spotlight: Luna Moth

Luna Moth

Luna Moth

If you’ve ever walked out your door in the morning and encountered a Luna Moth clinging to the underside of a light or on the screen door, you know what a delight it is to see these large, lime green moths. The Luna, known as the “moon moth,” is perhaps the most famous among giant silkworm moths. Its 4 ½-inch wingspan, together with the delicate wing coloration and the added grace of its tails, make it a striking creature to see. It ranges east of the Great Plains.


  • When the Luna hatches its first instar is 6 – 8 mm (.23inches) and grows to 65mm (2.5 inches) before pupating.
  • Luna Moths are only found in North America and is quite common throughout its range
  • Female Luna’s release a potent perfume by contracting muscles in the abdomen.  It is almost undetectable to humans, but the scent is detected by a male Luna up to a half a mile away.
  • Female Lunas prefer to deposit their fertilized eggs on hickory, birch, sweet gum or persimmon trees.
  • Luna’s deposit their eggs on trees where other species of moths have laid their eggs, making stiff competition for the caterpillars.

Giant silkworm moths are hard to spot because they prefer to fly high in the trees. The caterpillars are lime green with yellow bands, and red and silver tubercles (small, knob-like or rounded protuberances that sometimes bear a spine).

Luna Moth

Luna Moth

Celebrate Moth Week 201 by sharing your Moth sightings on NatureShare.

To find a Moth Week event near you visit Moth Week.

Spring Wildflowers


Monday, May 6th, 2013

Spring Wildflowers

What I’m looking forward to this spring…

On my two acre wooded lot in Woodstock, Vermont, the spring time treats me to three of my favorite wildflowers – Purple Trillium, Jack-in-the-Pulpit, and Wild Columbine.  The Wild Columbine is distinct from the Red Columbine of the west and prefers rocky, wooded, or open slopes and parts of my woods is perfect habitat.  Jack-in-the Pulpit prefers damp woods and grows in two spots.  Purple Trillium has a special place in my heart.  My dad transplanted several plants from the Adirondack Mountains in our backyard and they bloomed every spring for as long as my parents lived in the house (over 50 years) and I imagine that they are still blooming 20 years later in memory of my parents and brother.  I also love the regional names we have for this flower in the northeast, Wakerobin and Stinking-Benjamin.  I wonder who Benjamin was and why he was honored, having his name associated with this lovely wildflower. (Or was it his smell.)

Purple Trillium

Purple Trillium © Charlie Rattigan


Jack-in-the-Pulpit © Charlie Rattigan

Wild Columbine

Wild Columbine © Charlie Rattigan

Photo Essay: Brown Pelicans


Wednesday, May 1st, 2013

Photo Essay: Brown Pelicans by Charlie Rattigan

Boca Grande, Florida Gasparilla Island  (26.738520 , -82.264413)

Just after sunrise on April 10, 2013 nearly 100 Brown Pelicans, Laughing Gulls, and Common Terns began a feeding frenzy several meters off shore from the Gulf beach just south of Gasparilla Island State Park.  Of the many pelicans feeding, it was not unusual to see as many as five or six birds rise up and dive in quick succession.  The activity lasted well over an hour and was repeated the next day.  The weather was bright and sunny and the wind out of the east and calm.  It was only these mornings that I saw this behavior and suspect that when the wind shifted to a southwesterly direction the fish moved way from the shore.

Divining Brown Pelican

Divining Brown Pelicans © Charlie Rattigan

five pelicans

Brown Pelicans © Charlie Rattigan

knifing into the water

Brown Pelicans knifing into the water © Charlie Rattigan

Brown Pelican Birds

Brown Pelicans © Charlie Rattigan

pelican in various poses

Brown Pelicans © Charlie Rattigan

Pelican takes off

Brown Pelican takes off © Charlie Rattigan

Pelicans dive 1

Brown Pelicans preparing to dive © Charlie Rattigan

Nature Stories: Snowflake


Thursday, January 3rd, 2013
Snowfall in Vermont 12/27/12

Snowfall in Vermont 12/27/12

Anyone who has looked closely at a snowflake under a magnifying glass, or even with their naked eye, has an appreciation for the intricacy and delicacy of these frozen ice crystals that descend from the sky.  Exactly how do they form and why do they assume the shapes that they do?

Snowflake © Kenneth G. Libbrecht

Snowflake © Kenneth G. Libbrecht

According to physicist Kenneth Lebbrecht, in his book The Snowflake: Winter’s Secret Beauty, snowflakes and snow crystals are made of ice. As its name implies, a snow crystal consists of a single crystal of ice.  Snowflake is a general term that includes all shapes and combinations of snow crystals.  A snowflake can be a single snow crystal, or a conglomerate of crystals.

A snow crystal is not a frozen raindrop.  When raindrops freeze, they are referred to as sleet; the individual particles of ice lack the intricate patterns of snowflakes.  Rather, snow crystals form when water vapor in the clouds condenses directly into ice. As more vapor condenses, the ice crystal grows and develops, creating elaborate patterns.

Snowflake © Kenneth G. Libbrecht

Snowflake © Kenneth G. Libbrecht

There is a sequence of events in the formation of a snow crystal.  Evaporation from the ocean, lakes and streams, as well as the transpiration of plants and the expiration of animals puts a large amount of water vapor into the air.  When a mass of air cools, the water vapor it contains condenses out of it.  In summer, when this occurs next to the ground, we refer to the condensed water droplets as dew. When the air high above the ground is cooled, the water vapor condenses onto particles of dust, forming clouds full of water droplets.  In winter, the individual water droplets start to freeze around 14 degrees Fahrenheit. They don’t all freeze at once; gradually the water droplets surrounding the particles of ice evaporate into water vapor which then condenses onto the ice crystals, growing snow crystals.


Snowflake © Kenneth G. Libbrecht

Many snow crystals begin as hexagonal prisms – flakes with smooth facets, or sides, arranged in a hexagonal shape.  “Branches” then sprout at each of the six corners of this hexagonal crystal and as the surrounding water vapor condenses on them, they grow. Because the entire crystal passes through the same climatic conditions, the branches tend to grow in a similar pattern at a similar rate, creating the six-pointed star-shaped crystal, or stellar dendrite, that we are familiar with.  Many shapes, including columns, plates and needles, are formed.  Humidity, and particularly, temperature, affects the pattern of growth.  Snow crystals tend to form simpler shapes when the humidity is low, and more complex shapes at higher humidities. Even so, the majority of snowflakes are not symmetrical.  Within a given cloud, different snowflakes are blown in different directions, encountering different temperatures, which results in slightly different shapes.  Thus, no two snowflakes are identical.

Snowfall © Mary Holland

Snowfall © Mary Holland

Did you know? Three Rivers Petroglyph Site


Friday, November 16th, 2012

Did you know? 
Three Rivers Petroglyph Site

Three Rivers Petroglyphs

The Three Rivers Petroglyph Site is one of the few locations in the Southwest set aside solely because of its rock art. It is also one of the few sites giving visitors such direct access to petroglyphs. The number and concentration of petroglyphs here make it one of the largest and most interesting petroglyphs sites in the Southwest. More than 21,000 glyphs of birds, humans, animals, fish, insects and plants, as well as numerous geometric and abstract designs are scattered over 50 acres of New Mexico’s northern Chihuahuan Desert. The petroglyphs at Three Rivers, dating back to between about 900 and 1400 AD, were created by Jornada Mogollon people who used stone tools to remove the dark patina on the exterior of the rock. A small pueblo ruin is nearby and Sierra Blanca towers above to the east. A detailed petroglyph guide is available at the Three Rivers Petroglyph Site.

Three Rivers Petroglyphs
  • Hiking
  • Back-packing
  • Camping
  • Picnicking
  • Prehistoric Interpretation

A rugged half-mile trail begins at the visitor shelter and links many of the most interesting petroglyphs. Another short trail begins on the east side of the picnic area and leads to the remains of a Mogollon village, whose inhabitants were likely responsible for the petroglyphs. Occupied for about 400 years, the site was partially excavated in 1976. On the village site, there are foundations of three types of prehistoric buildings. A small pueblo ruin is nearby and Sierra Blanca towers above to the east. Just up the road is Three Rivers Campground and an entry point into the Lincoln National Forest.



Remarkable Nature Places: Edwin B. Forsythe National Wildlife Refuge


Friday, November 16th, 2012
View of the Wildlife Drive

View of the Wildlife Drive at Edwin B. Forsythe National Wildlife Refuge. Photo courtesy of U.S. Fish and Wildlife Service

Edwin B. Forsythe National Wildlife Refuge

Forsythe (Brigantine),  New Jersey

These thirty-six thousand acres of coastal marsh are a birder’s dream. Probably there is no place certainly no place on the Northeast and mid-Atlantic coast where birders can find such large numbers, variety, and the occasional rarity. And what is here is unusually accessible, from a wildlife drive on top of a dike that divides salt marsh from freshwater impoundments.

October can bring a peak of more than 150,000 waterfowl of two dozen or so species, which may linger into midwinter depending on freeze-up in the coastal bays.

Ghost Crab

Ghost crab (Ocypode) posing for a picture at Little Beach, NJ. Photo courtesy of U.S. Fish and Wildlife Service

None are more spectacular than the Snow Geese which can seem to fill the air with their cries. Thousands fly in at a height of less than 50 feet against a crimson sunset, returning from feeding in the marshes to spend the night in the pools. They nearly cover the water with their white bodies.

More than 80,000 Brant may come in — 20% of the Atlantic population of this small dark goose which leads such a precarious existence — nesting in a small area north of the Arctic Circle and with a diet so limited they nearly became extinct during an eelgrass blight in the 1930s. (Luckily eelgrass does well here now.)

Ducks will include Northern Pintails, Gadwalls, American Wigeon, Blue-winged Teal, Green-winged Teal, Northern Shovelers, Ruddy Duck and Black Ducks, which also nest — and perhaps among all these a rare Eurasian Wigeon and Ross’ or Barnacle Goose, a Ruff, or an Ivory Gull.

Endangered Peregrine Falcons are around most of the year. Two pairs which nest on the refuge usually bring off several youngsters each from nesting towers constructed for the peregrine, and others appear to hunt, sometimes thrilling a lucky observer with a lightning stoop on a migrating duck or a threatening dive on a marsh harrier invading its territory. (Fierce Great Horned Owls sometimes prey on the peregrines at night).

Snowy Egret

Snowy Egret at Wildlife drive. Photo courtesy of U.S. Fish and Wildlife Service.

Pair of Osprey

Pair of Osprey in their nest at Wildlife Drive. Photo courtesy of U.S. Fish and Wildlife Service

Beautiful tall wading birds can be almost anywhere along the water’s edge — Great Blues most of the year and Little Blue HeronsSnowy Egrets and Great EgretsTricolored Heron and Black-crowned Night-Herons, and, less obviously, American Bitterns from April to October. In May and June Glossy Ibises are everywhere — hundreds of them, offering an unusual opportunity to see this retiring, darkly iridescent species.

The clattering call of the Clapper Rail is commonly heard even when the bird itself is too shy to be seen. Ospreys are here from March to November and an occasional bald eagle comes by in winter.

Warblers and songbirds make an appearance around upland walking trails around the same time Horseshoe Crabs show up on the beach to mate and lay their eggs. This coincides with the full moon and the highest tides of May — a phenomenon that attracts Ruddy Turnstones, Dunlins and other shorebirds by the thousands to fatten up on the eggs for their continuing journey northward to nesting grounds.

Grasshopper Sparrows, sharptailed and Seaside Sparrows stay to nest, as do Forster’s, Least, Caspian and Gull-billed Terns. Canada Geese bring downy broods to pose for photographers on the dikes.

The wetland habitat does not support a large mammal population but some are here — raccoon, skunk, weasel, muskrat, fox, both red and gray, and otter. One of the best ways to see otters playing — which is what they mostly do — as well as red fox hunting is to wait and watch early at the northwest corner of the wildlife drive.

The beautiful rare Pine Barrens Treefrog, bright green with plum body stripes, lives on a bog recently added to the refuge.

View of the Wildlife Drive

View of the Wildlife Drive at Edwin B. Forsythe National Wildlife Refuge. Photo courtesy of U.S. Fish and Wildlife Service

The refuge includes 6,000 acres of wilderness with such nowadays-rare features as several thousand acres of pristine salt marsh accessible by small boat only, offering fascinating views of estuaries and salt marsh; and the undeveloped coastal barrier beaches of Holgate unit and Little Beach Island, New Jersey’s only offshore island not accessible by road. Here one finds plants rare elsewhere; also the threatened Piping Plover as well as colonies of Black Skimmers and least terns. To protect them both the Holgate Unit and Little Beach Island are closed to public use during nesting, and the fragile dune area is closed all year.

The Barnegat Unit, more than 14,000 acres of salt marsh habitat, is accessible by boat or by viewing from several adjacent roads; otherwise it has no public use facilities.

How to Get There
From Absecon, take Route 9 north about 4.5 miles to Great Creek Road in Oceanville. Turn right there to refuge office. (The Intracoastal Waterway bisects the refuge and boat landings are nearby.)

Sunrise to sunset. Office 8-4 weekdays, volunteers available for information on busy fall and spring weekends. Entrance fee.

Best Times to Visit
Spring and fall.

What to See
Great numbers and variety of bird species.

What to Do
Two self-guided walking trails; eight-mile wildlife drive surrounded by salt marsh with great diversity of birds from both fresh and salt estuary habitat in view simultaneously; observation towers; limited small boat launch facility at Scott’s Landing.

Where to Stay
— Motels — On Route 9 and 30, around Absecon.
— Campgrounds — At Wharton State Forest and Bass River State Forest, adjacent to refuge on north.

Variable all year — come prepared for possibility of change. Winter ice can close wildlife drive — best call ahead.

What to Take and Wear
— Insect repellent in summer.
— Sturdy waterproof footgear a good idea on the trails.
— A warm jacket November through March.

Points of Interest Nearby
— Wharton State Forest (see campgrounds) — part of interesting Pine Barrens.
— Cape May Bird Observatory.
— Stone Harbor near Cape May worth a visit for its fascinating heronry, located right in the center of town.

For More Information

Forsythe (Brigantine) National Wildlife Refuge
P. O. Box 72
Great Creek Road
Oceanville, New Jersey 08231

Phone: 609-652-1665

Fax: 609-652-1474


Update as of Monday, November 5 at 4:00 p.m.

Most areas of Edwin B. Forsythe National Wildlife Refuge will remain closed to public use until damage and repair needs are assessed in the wake of Hurricane Sandy. This includes the Wildlife Drive in Galloway, Holgate beach on Long Beach Island, and the deCamp Wildlife Trail in Brick Township.

Water crested over the Wildlife Drive in Galloway and it sustained significant damage during the storm.  Extensive assessments will need to take place before a timeframe for repairs can be estimated.

Trails adjacent to the Wildlife Drive and the Visitor Information Center are currently closed, and will remain closed until public safety can be ensured. Other areas of the 47,000-acre refuge will be re-opened as soon as possible.

Nature Stories: Tracking the Family Dog


Friday, November 16th, 2012

Coyotes © NatureShare

Nature Stories: Tracking the Family Dog by Mary Holland

Identifying tracks in the snow can be daunting, especially if the snow is light and fluffy, leaving few details of the animal’s foot.  However, on days when snow conditions allow nails and pads to be seen, there are ways of finding out what creatures have been active.  While the dimensions of a track, as well as the length of the stride of an animal and the width of its trail are crucial aids to identification, there are other traits to take into consideration. A primer on the dog family illustrates the kind of observations that are helpful in identifying tracks.

There are four members of Canidae, the dog family, that you may encounter in the Northeast:  domestic dog, gray fox, red fox and coyote.  All of these canids have four toe pads that register in the substrate.  They all have thick, unretractable nails, some of which also usually register. The track they leave is, as a rule, longer than it is wide, creating an oval impression (as opposed to a cat’s roundish track).  In most cases, you can imagine drawing an “X” in the spaces between the toe pads and the large metatarsal, or heel, pad behind them.  All members of the dog family share these characteristics, which can make their tracks relatively challenging to distinguish from one another.

There are a few helpful traits for telling a domestic dog, fox and coyote track apart.  To begin with, although their ranges do overlap, you often find wild canid tracks on man-made trails and back roads, far from where domestic dogs would tend to travel.  A look at the trail that the tracks make will help determine whether it’s a domestic dog or a wild canid.  Because they know they don’t have to worry about filling their bellies, dogs are often quite aimless when they are out and about; their tracks tend to be less purposeful and wander all over the place.  Foxes and coyotes are intent on finding their next meal, and don’t waste precious energy taking unnecessary steps.  Thus, their trails often are less sloppy than domestic dogs’ and much straighter. In addition, foxes and coyotes have a tendency to direct register – place their hind feet exactly where their front feet have been.  Dogs sometimes do this, but more often the front and hind foot tracks are not precisely on top of one another.  A close look at the details of the track of a dog will show that the toes are splayed out, the nail of each toe pointed in a different direction.  The toes of foxes and coyotes are usually tight together, with the inner two pointing straight ahead, and the outer two toes somewhat behind them.

Distinguishing fox from coyote tracks is a bit more difficult. The width of a fox’s trail (straddle) is narrower than that of a coyote, as foxes are considerably smaller.  Foxes are very agile, and their tracks often go along fallen logs and stonewalls (gray foxes even climb trees); coyotes tend to be more grounded. Individual fox tracks have a delicate appearance, even in snow.  They are small, and there is quite a bit of space between their toe pads and the metatarsal pad.  Because they are very hairy, red fox feet do not always reveal this in snow, but in mud and in good winter tracking conditions, it is possible to see the imprint of a raised ridge on the back of the front foot’s metatarsal pad.  This ridge can be straight or slightly curved, like a chevron, and can help distinguish the red fox from the gray.  Both species of foxes have semiretractable nails, whereas coyotes don’t retract their nails.  Consequently, coyote tracks will almost always show at least one or two nail marks – fox tracks may not.

Coyote Tracks © NatureShare


Nature Stories: The Great Horned Owl


Friday, November 2nd, 2012

Nature Stories: The Great Horned Owl

Great Horned Owl

Great Horned Owl adult,Eastern © Johann Schumacher/VIREO

The Great Horned Owl is an impressive bird, measuring up to 25 inches from head to tail, with a four-foot wingspread.  In North America, only the Snowy Owl and the Great Gray Owl are sometimes larger.  Even if heard and not seen, the great horned owl’s stature is discernible.  The four to eight resonant “hoots”  of both males and females can be heard for a considerable distance, even though they have a slightly muffled quality.   Not only its impressive size distinguishes this bird.  According to the Cornell Laboratory of Ornithology, the great horned owl has the most extensive range, largest variety of prey and most variable nesting sites of any owl in North America.

Great Horned Owl

Great Horned Owl adult with owlets, Southwestern © John Cancalosi/VIREO

Hard as it may be to believe, the great horned owl’s courtship begins as early as January in the Northeast, and the female is often sitting on eggs by February. Photographs have been taken of great horned owls incubating their eggs while covered with snow.  These birds do not usually build their own nest, rather they seek shelter in which to lay their eggs, primarily in the unoccupied tree nests of other species of birds, particularly the abandoned stick nests of diurnal birds of prey.  Red-tailed hawk nests are preferable, but those of crows, ravens, herons, eagles, ospreys and squirrels are also used.  Occasionally they will nest inside a tree cavity or on top of a dead stump.

Any owl nesting this early in the year has to have a hardy constitution, which the great horned owl most certainly does.  Research shows that they are able to incubate eggs successfully, keeping them at a toasty 99 degrees Fahrenheit, when the ambient temperature is -27 degrees F.

While rabbits and hares are their favored prey, great horned owls also hunt other birds such as ruffed grouse and ducks, snakes, amphibians, insects and even skunks and porcupines.  Anyone who has the good fortune of being within smelling distance of a great horned owl, has a good chance of detecting the distinctive odor of a skunk, as the leg feathers of the predatory owl absorb the smell of this odoriferous prey.

Great Horned Owl

Great Horned Owl adult, Pacific © Gerrit Vyn/VIREO

One of the easiest ways to locate a great horned owl is to follow the cries of mobbing American crows and blue jays, which often tend to gather and harass owls during the day.  At this time the great horned owl is trying to rest, and often sits silently, attempting to ignore the raucous mob surrounding it.  Frequently, roosting great horned owls can be found perching close to the trunk of a tree, in the middle of its crown.

Remarkable Nature Places: Morley Nelson Snake River Birds of Prey NCA


Friday, November 2nd, 2012

Arial Shot of Morley Nelson Snake River Birds of Prey NCS Photo courtesy of BLM

Remarkable Nature PlacesMorley Nelson Snake River Birds of Prey National Conservation Area

Crags and crevices, the deep canyon of the Snake River, thermal updrafts, and a broad plateau rich in small wildlife sustain the greatest concentration of nesting birds of prey in North America.

Congress established the Snake River Birds of Prey NCA in 1993 to recognize and perpetuate the area’s wildlife values.  Part of the BLM National Landscape Conservation System (NLCS), the NCA encompasses 485,000 acres of public land along 81 miles of the Snake River in southwestern Idaho.  The BLM manages the area to preserve its remarkable wildlife habitat while providing for other compatible uses of the land, so that birds of prey flourish here as they have for thousands of years.

Morley Nelson Snake River Birds of Prey NCS Photo courtesy of BLM

Nesting Raptors

·       American Kestrel

·       Ferruginous Hawk

·       Golden Eagle

·       Northern Harrier

·       Osprey

·       Prairie Falcon

·       Red-tailed Hawk

·       Turkey Vulture

·       Barn Owl

·       Burrowing Owl

·       Great Horned Owl

·       Long-eared Owl

·       Northern Saw-whet Owl

·       Short-eared Owl

·       Western Screech Owl

·       Swainson’s Hawk

Migrating Raptors

·       Bald Eagle

·       Gyrfalcon

·       Merlin

·       Northern Goshawk

·       Peregrine Falcon

·       Rough-legged Hawk

·       Sharp-shinned Hawk

·       Cooper’s Hawk

Morley Nelson Snake River Birds of Prey NCS Photo courtesy of BLM

General Raptor Facts

Size Difference

Female raptors are generally larger than the males. The reason for this size difference is really unknown, but scientists theorize that it could relate to the female spending more time on the nest and can protect the young from larger predators. Another idea for this difference is that it allows for a greater diversity of prey to be taken by the adult pair.


Raptors have three eyelids! They have a top and bottom eyelid plus a third, transparent eyelid which closes laterally across the eye. This special eyelid is called a nictitating membrane and is used to;

  • keep the eyes moist,
  • protect the eyes during flight, and
  • protect the eyes when feeding themselves or their young.

When humans close their eyes to blink or sleep the upper eyelid closes. Depending on the species, raptors may close the top eyelid, the bottom eyelid, or both.

An additional form of eye protection in many raptors is a bony shield, called the superciliary ridge, that projects above the eye. This ridge acts like a visor for protection from the sun and also protects the eyes from injury while hunting. It also gives raptors a menacing appearance.


Nesting habits of raptors vary among species. Some examples of these differences include:

  • not building a nest, but using stick nests or cavities created by other birds,
  • nesting and laying eggs in sand or gravel, depressions, or scrapes,
  • nesting and laying eggs on the ground,
  • nesting and laying eggs on cliff faces or in treetops,
  • nesting and laying eggs in ground burrows of mammals (burrowing owls).
  • For raptor species that build nests, typically the female constructs the nest while the male provides the material. Many raptors build a new nest each year, while others, particularly large raptors, will reuse old nests or alternate between a number of nests.


Raptor eggs are typically large, rounded or oblong ovals, and vary in color. The number of eggs laid depends on the raptors size. Larger raptors lay fewer eggs than smaller raptors. It is believed that larger raptors live longer and need fewer eggs or young to sustain the viability of their species, while the opposite is true for smaller raptors.

Morley Nelson Snake River Birds of Prey NCS Photo courtesy of BLM

There may be a two to three day lapse between laying each egg, and the adult may not begin incubation until all the eggs are laid (owls begin incubation immediately after the first egg is laid). The female does the incubating while the male provides food for her. The period of incubation varies with the size of a bird. For owls, hawks, and falcons there is usually a 26 to 35 day incubation period, while eagles and vultures will incubate from 36 to 50 days. Raptors in temperate climates breed in spring and summer.

After an eggshell is first cracked, it may take one to two days before hatching is complete. Raptor chicks grow quickly, doubling their birth weight in only a few days. The length of time a raptor spends from hatching until it is ready to fledge (fly on its own), depends on its size. Larger raptors stay in the nest from two to three months, while smaller raptors stay three to four weeks.

Morley Nelson Snake River Birds of Prey NCS Photo courtesy of BLM

Did You Know: The Northern Lights


Friday, November 2nd, 2012
Northern Lights

Toklat Aurora Borealis Photo Courtesy of NPS/Jacob W. Frank

Did You Know? The Northern Lights

Here’s the science behind this remarkable visual event.

The aurora borealis (Northern Lights) occurs when a coronal mass ejection (CME), a massive burst of solar wind and magnetic fields, interacts with elements in the earth’s atmosphere. Coronal mass ejections are often associated with other forms of solar activity, most notably solar flares. Near solar maxima the sun produces about three CMEs every day, whereas near solar minima there is about one CME every five days.

Northern Lights

Aurora – Ghost Walk Photo Courtesy of NPS/Tim Rains

Solar winds stream away from the sun at speeds of about 1 million miles per hour and reach the earth roughly 40 hours after leaving the sun. ­As the electrons enter the earth’s upper atmosphere, they will encounter atoms of oxygen and nitrogen at altitudes from 20 to 200 miles above the earth’s surface. The color of the aurora depends on which atom is struck, and the altitude of the meeting.

Northern Lights

Aurora Sets the Trees Aflame Photo Courtesy NPS/Tim Rains

• Green – oxygen, up to 150 miles in altitude
• Red – oxygen, above 150 miles in altitude
• Blue – nitrogen, up to 60 miles in altitude
• Purple/violet – nitrogen, above 60 miles in altitude

Northern Lights

Aurora Over the Trees Photo Courtesy NPS / Jacob W. Frank

All of the magnetic and electrical forces react with one another in constantly shifting combinations. These shifts and flows can be seen as the auroras “dance,” moving along with the atmospheric currents.

The auroras generally occur along the auroral ovals, which center on the magnetic poles and roughly correspond with the Arctic and Antarctic circles. The lights can be visible at lower latitudes when solar activity is high.

Check here for current aurora activity and the aurora forecast.

Northern Lights

Aurora Borealis Over Savage Cabin Photo Courtesy of NPS / Jacob W. Frank