NEW AND IMPROVED: Turn your iPhone or iPod Touch into a field-tested global satellite tracker. The Satellite Flybys app now works in all countries. | | | AURORA WATCH: High latitude sky watchers should be alert for auroras. A coronal mass ejection (CME) is expected to deliver a glancing blow to Earth's magnetic field on April 17th. NOAA forecasters estimate a ~30% chance of geomagnetic activity when the cloud arrives. NO CONTRAILS, GREAT SUNSETS: Normally, the sky around this radio air traffic control tower near Frankfurt, Germany, is criss-crossed by contrails. "But not today," says photographer Helmut Marten. "Because of the dust clouds from Iceland's Eyjafjallajokull volcano, almost all of the air traffic over northern Europe has come to a halt." Hard and sharp-edged volcanic dust is hazardous to aircraft, clogging engines that suck it in, and pitting windows that pilots need to see through. According to Eurocontrol, the intergovernmental body that manages European air travel, about 16,000 flights across Europe have been canceled. Stranded passengers have one consolation--sunrises and sunsets of rare beauty. Browse the links below for examples. volcanic sky shots: from René of Schiphol, Amsterdam, Netherlands; from Manuel ten Hake of Zoetermeer, The Netherlands; from Vincent Phillips of Speke, Liverpool, England; from Toine Kuiper of Leende, Netherlands; from Jeffrey Berkhout of Nibbixwoud, Netherlands; from Katie-Anne Fitzgerald of Belton North Lincolnshire UK; from Alan C Tough of Elgin, Moray, Scotland VOLCANIC LIGHTNING: It is well known that volcanic eruptions produce strong lightning. Less well known is why? Ordinary lightning in thunderstorms is not fully understood; volcanic lightning is even more of a mystery. To investigate, a team of researchers from New Mexico Tech has traveled to Iceland to monitor the Eyjafjallajokull volcano--and they have found it crackling with electricity: "On the evening of April 16th, there were some small eruptions producing ash clouds up to about 6-7 km, with lightning," says photographer Harald Edens. "The sky was nice and clear, so I was able to photograph the bolts from the town of Hvolsvollur using my Nikon D700 and a 80-200/2.8 lens." Photography is one way to monitor volcanic lightning, but the technique has limits: Ash clouds are able to hide the flashes; lightning is not always visible in daylight; glowing lava competes for attention; and so on. Radio receivers can do a better job. Lightning emits impulsive radio bursts which can be measured and counted, day or night, even through clouds of ash. "We are deploying a six-station lightning mapping array around the Eyjafjallajokull volcano," says Edens. Their analysis of the radio "crackles" could reveal much about the inner workings of volcanic lightning. April Northern Lights Gallery [previous Aprils: 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002] |