Public Lecture: "Earth's Ignorosphere"

IrishMetSoc

Public Lecture: "Earth's Ignorosphere"
By Frank Mulligan, NUI Maynooth


When? Thursday November 26th 2009


Where? Trinity College Dublin, Botany Lecture Theatre (near the rugby pitch)http://www.tcd.ie/Maps/assets/pdf/tcd-main-campus.pdf


For more information see www.irishmetsociety.org

IrishMetSoc

"The Middle Atmosphere - Earth's Ignorosphere"

Redsunset

The space shuttle Columbia's troubles began as it dropped like a meteor from orbit into a mysterious and poorly understood atmospheric region that scientists have dubbed the "ignorosphere."

The Concorde flew in the bottom of this region at more than 11 miles above the Earth's surface. Nothing but a rocket can fly at its upper limit of 53 miles. The "ignorosphere" encompasses the mesosphere and upper stratosphere.

Invisible clouds, strange electrical flashes called red sprites and blue lightning bolts that strike upward from the tops of clouds inhabit the thin air. This is the place where falling stars are made.

The "ignorosphere" earns its nickname from the fact that you can't get there from here without a rocket. It is too high for weather balloons and too low for satellites to dip down to gather information.

Much of what is known about the upper atmosphere comes from measurements collected during more than 100 re-entries by space shuttles since the first launch of the Columbia in 1981.

A report by NASA scientists describes concerns about the impact of upper atmospheric phenomenon on the space shuttle:

• Transparent clouds, called "noctilucent" clouds, float 50 miles above Earth and are visible only at twilight. These silvery cirrus clouds form at the edges of much larger clouds. Models of shuttle impacts with them "vary from trivial to catastrophic" according to the report, which says "the most severe effect of entry through a noctilucent cloud would probably be the erosion of the thermal protection system during the most critical heating region." That critical heating region is where Columbia was destroyed. The agency plans its re-entry paths to avoid regions thought prone to these clouds.

• Red sprites are electrical discharges in the upper atmosphere. They occur over thunderclouds and have been considered to pose less than a one in 100 risk to the shuttle.

• Density shears are patches of thicker-than-expected air that can increase the shuttle's roll and pull on one wing. On a Columbia mission in 1992 and an Endeavor mission in 1993, hitting such patches forced them to use up its fuel for the thrusters that help keep it on course during re-entry.

• Blue jets are upward lightning strikes. In 1998, Lyons and a team of scientists reported one that was sparked by a meteor