Mystery Of Powerful Lightning At Sea Not Solved Completely

The mystery of why most of the most powerful lightning on Earth happens over the oceans isn’t solved, but a few of the usual suspects are no longer in custody.

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It isn’t an instrument error, as some hypothesized. Nor is it the relative rarity of cloud-to-sea lightning allowing charges to build. And when it comes to cloud top heights, size apparently doesn’t matter.

It’s possible the increased presence of salt in the atmosphere plays a role, but if that is the case it probably has an accomplice. The evidence implicates ice crystal size, although air flowing back and forth along the land-sea boundary might also be involved.
“There isn’t one single mechanism that by itself justifies the stronger peak current we see in cloud-to-ground lightning over the oceans,” said Dr. Themis Chronis, a research scientist in the Earth System Science Center at The University of Alabama in Huntsville (UAH). “This process isn’t as simple as we previously thought.”

Results of this research at UAH, NASA and the Universities Space Research Association (USRA) were published recently in the Journal of Geophysical Research.

Scientists have known since the early 1990s that the initial return stroke – the flash when a leader or electric channel connects a cloud to the surface – usually has a more powerful current over the oceans than lightning over dry land. While there have been hypotheses about why that should be the case, there was no generally accepted explanation.

Chronis, NASA’s William Koshak and Bill McCaul with the USRA used lightning data from the National Lightning Detection Network to create datasets for four coastal areas: along Lake Michigan, the mid-Atlantic, the Florida peninsula and the upper Gulf Coast. Then they tracked the strength and location of each lightning strike over each of those locations.

They found a type of power curve along each of the oceanic shorelines, with the relative strength of lightning strikes starting to rise just a bit inland and continuing to rise as the strikes move out to sea until the instruments no longer are reliable. The strongest lightning was along the Gulf of Mexico during the wet season.

There was, however, no such differentiation along or over Lake Michigan. Lightning over the fresh water lake was no more powerful than lightning over the surrounding land.

So it must be the increased concentration of salt – an electrical conductor – being transported from the sea into the atmosphere, right?
Well, not entirely.

“Salinity isn’t altogether out of the question. Yet,” said Chronis.

Salt is an especially dicey suspect for causing powerful lightning because atmospheric concentrations of salt rise and fall with the seasons, but not in synch with the seasonal rise and fall of powerful lightning strokes.

It is known that storms over the oceans (and slightly inshore) tend to create larger ice crystals than inland storms. Large ice crystals can hold a more powerful electric charge, but that doesn’t explain why that extra charge isn’t discharged in routine amounts through routine lightning.

And, while the size of ice crystals might vary as much as 10 percent across the land/sea boundary, the differences in the electric discharge in lightning strokes can vary by 25 to 30 percent.

It is puzzling.

For now the cause of powerful oceanic lightning will, apparently, remain a mystery. This latest research might imply increased salinity and large ice crystals in combination with storm physics could be the cause. Any conclusive theory will probably wait for additional research and data provided by new instruments, such as the Geostationary Lightning Mapper (GLM). GLM is scheduled for launch later this year aboard NOAA’s Geostationary Operational Environmental Satellite – R Series (GOES-R) weather satellite.

(NEW) Scientists Detect Unexpected Drop in the Magnetic Field of X-Ray Pulsar

A team of scientists has recently presented evidence of an unexpected drop in the observed magnetic field of an accreting pulsar designated V0332+53. This downturn, observed after the pulsar underwent a bright, three-month-long X-ray outburst, could yield important information on how the accreted mass settling on the surface of a neutron star affects its magnetic field. The findings are detailed in a paper published online on Apr. 26 in the arXiv journal.

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V0332+53 is an accreting pulsar emitting X-ray radiation, with a spin period of 4.4 seconds. It orbits an early type companion star in an eccentric orbit of about 34 days. Significantly, this pulsar shows sporadic giant X-ray outbursts lasting several weeks, followed by years-long intervals of dormancy.

These X-ray outburst were observed in 1989, between November 2004 and February 2005, and between June and September 2015. The latest outburst drew the attention of a team of researchers, led by Giancarlo Cusumano of the Institute of Space Astrophysics and Cosmic Physics in Palermo, Italy. Using the Burst Alert Telescope (BAT) and the X-Ray Telescope (XRT), both mounted on NASA’s Swift spacecraft, the astronomers were able to observe the pulsar in soft X-ray and high-energy bands.

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By studying the results, the team detected a noteworthy drop in the observed magnetic field between the onset and the end of the outburst.

“The comparison of the XRT profiles in the soft X-rays provides a hint against the hypothesis of a geometrical beam variation. If, on the other hand, the line-forming region is the same at equal luminosities, the observed difference in the cyclotron energy corresponds to a difference in the magnetic field of about 1.7 ×1011 G,” the researchers wrote in the paper.

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The findings could be crucial for our understanding of matter accretion processes in neutron stars and could provide new insights on pulsars’ X-ray outburst events. According to the research, the magnetic field of neutron star drives the accreting matter along its field lines towards the magnetic polar caps, forming an accretion column, where matter is followed up by radiative processes that produce X-rays.

Notably, the drop in the magnetic field, as described in the latest paper, wasn’t observed after previous outbursts. The researchers found out that although the total mass accreted at the end of the 2004-2005 and the 2015 outburst is similar, during the 2004-2005 event, a higher luminosity was reached earlier. They also concluded that decay of the magnetic field is not directly proportional to the total accreted mass.

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Moreover, the scientists hypothesize that the cause of the significant decay of the magnetic field through accretion observed at V0332+53 could be due to “diamagnetic screening.”

“In this hypothesis, the accreting plasma builds up to form a magnetically confined mound, where the gas pressure balances the magnetic stresses. This would produce, as an overall effect, a distortion of the field lines observed as a decrease of the field component along the accretion column,” the paper reads.

However, as the team noted, the lack of coverage in the first ten days of the outburst doesn’t allow them to confirm this theory.

Wild Winds Whip New England Ahead Of Major Snowstorm

The winter storm battering parts of New England Monday isn’t expected to drop 2 to 3 feet of snow in one go, but officials warn that wild winds and blizzard conditions could still cause power outages and tree damage – and make for an uncomfortable, if not dangerous, commute.

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The National Weather Service has issued blizzard warnings from the south of Boston to the South Shore, while areas of eastern New England – including Boston, Hartford, and Providence – are under winter storm warnings. Snow, which began after 8 a.m., may fall at rates of more than an inch an hour in parts of eastern New England, The Weather Channel reports.

But “[i]t’s not just the snow we are talking about – very strong winds, coastal flooding concerns – there could be some power outages, especially south of Boston,” said Cindy Fitzgibbon, meteorologist for Boston’s WCVB 5.

“The heaviest snow will fall this morning into mid/late afternoon across the region,’’ forecasters noted, according to the Boston Globe. “The greatest impact from this storm will not be specific snow amounts, but blizzard conditions.’’

The winter storm, dubbed Mars by The Weather Channel, is a result of a low pressure area off the East Coast – an area that went through what meteorologists call “bombogenesis,” or a sudden central pressure drop of at least 24 millibars in 24 hours.

“ ‘Bombogenesis’ follows from ‘cyclogenesis,’ which refers to the development of a cyclone,” wrote Stu Ostro, a senior meteorologist with The Weather Channel. “Bombs are so named because of the rapidity with which they develop, which evokes explosiveness, and the power that they usually attain once they have gone through the intensification phase specified in the definition.”

Winds of up to 45 miles per hour could blow through eastern New England, while the gusts could hit up to 65 miles per hour on Cape Cod.

Boston Public Schools and dozens of other public and private colleges have canceled classes Monday. The Massachusetts Port Authority has also warned travelers to check their itineraries before heading to Boston’s Logan International Airport, noting that some airlines “have already begun cancelling a number of flights and may be making accommodations for those impacted passengers.”

Massachusetts Gov. Charlie Baker also asked residents to stay off the roads when possible.

Storm Imogen: Britain Faces 80mph Winds And Heavy Rain

Britain is to be hit by 80mph winds and heavy rain on Monday as Storm Imogen, the ninth major storm this winter, sweeps in from the Channel.

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The Met Office has issued amber “be prepared” weather warnings for much of the south-west and yellow “be aware” warnings stretch from southern Wales to the Thames estuary.

Storm Imogen comes at the end of a wet winter in which storms Henry, Gertrude, Frank and Desmond also battered the UK. The Met Office only started naming storms in 2015.

The warnings will be in place from 3am until 6pm on Monday and exposed areas on the south coast are on alert for winds of 80mph. The Met Office has warned that there could be “very large waves”, especially along the north coast of Cornwall and Devon.

Forecaster Craig Snell said: “We have issued a broad yellow warning of wind that encompasses Cardiff, Bristol and into the Thames estuary. There is an amber warning for wind mainly focused on Devon and Cornwall but stretching into central England on Monday morning.

“This means people should be prepared for disruption to travel on roads, rail, bridges and ferries and we could see possible damage to structures and downed trees risk affecting power. The wind will be combined with some hefty showers with some thunder along the south coast.”

There remains some uncertainty about how far north and east the strongest of the winds will extend, but gusts are expected to ease up on Tuesday. There is forecast to be a drier, quieter and colder interlude for many on Wednesday before more wind and rain follows later in the week.

South West Trains said it was planning to run a normal weekend timetable on all routes but that the risk of trees and debris being blown onto the railway might require the train line to “make adjustments to trains in certain areas”.

“In particular, the first trains to run over tracks may need to be cancelled to allow us to ensure these routes are clear and safe to run passenger services,” the statement read. “There may also be changes in the number of carriages to some services.”

The British Met Office and its Irish counterpart Met Eireann last year started following the approach taken by the US National Hurricane Centre and giving storms names in order to better communicate with the public.

Names are given in alphabetical order, though the letters Q, U, X, Y and Z are not used. The two Met offices released the official list of storm names in October and the next storm to hit the UK will be named Jake.