Japanese team sees gamma-ray pulse before lightning flash

First the gamma rays, then the flash

First the gamma rays, then the flash

Physicists in Japan have made the best study yet of the gamma rays that are produced in the minutes leading up to a lightning flash. In addition, the team also observed for the first time emissions that ended abruptly less than a second before the exact moment the flash occurs. The finding provides important information about the relationship between the mysterious atmospheric accelerators that produce the gamma rays and the lightning that we see in the sky.
Physicists have known for some time that gamma rays are sometimes produced when lightning strikes. Indeed, gamma-ray pulses from thunderclouds that vary in length from sub-millisecond to several minutes have been detected for the last 30 years. Most researchers agree that there are two types of bursts: very short, higher-energy bursts that coincide with lightning; and longer, lower-energy pulses that are sometimes not associated with a specific lightning event. While all of these bursts are thought to be created when charged particles are accelerated by the huge electric fields that build up in a thundercloud, the exact mechanism – or mechanisms – that produce them remains a mystery.
In this latest study, Harufumi Tsuchiya of the RIKEN High-energy Astrophysics Laboratory and colleagues at several other Japanese institutes looked at data collected in 2010 by the Gamma-Ray Observation of Winter THunderclouds (GROWTH) experiment at the Kashiwazaki-Kariwa nuclear power plant. The experiment includes several different gamma-ray detectors that are used in tandem with plastic detectors – the latter ensuring that charged particles such as muons are not mistaken for gamma rays. The system detected gamma rays at energies between 40 keV and 30 MeV…..
…. Read more at http://physicsworld.com/cws/article/news/2013/jul/10/

Redefining the ampere with the help of graphene?

Electron pumps made from graphene work 10 times faster than similar pumps made from conventional 3D materials and can be used to generate larger currents. (Courtesy: M Connolly)

Electron pumps made from graphene work 10 times faster than similar pumps made from conventional 3D materials and can be used to generate larger currents. (Courtesy: M Connolly)

The world’s first single-electron graphene pump has been built by researchers at the UK National Physical Laboratory and the Cavendish Laboratory in Cambridge. The device could be used to redefine the standard unit of current, the ampere, in terms of the electron charge – a fundamental constant of nature.
The international system of units (SI) is made up of seven base units, which are the metre, kilogram, second, kelvin, ampere, mole and candela. The ampere, volt and ohm are the three fundamental units of electricity.
Although physicists have already come up with modern ways to represent the volt and ohm (through measurements of the Josephson voltage and quantum Hall resistance, respectively), there is no equivalent for the ampere. Indeed, today, the ampere is defined as the current which, when flowing through two parallel conductors one metre apart, exerts a certain force between the conductors. Directly realizing such a macroscopic definition of current is experimentally difficult, and the accuracy of the result also depends on other base units, such as the kilogram, which drifts with time.

Enter SEPs

Ideally, a new definition of the ampere would be based on an extremely accurate source of electric current, capable of delivering one electron at a time. A single-electron pump (SEP) could be ideal in this respect because it produces a flow of individual electrons by shuttling them into a quantum dot and emitting them precisely one at a time. A good SEP also pumps the electrons quickly, so a sufficiently large current is generated.
Until recently, two types of SEP were promising contenders: tunable barrier pumps made from semiconductors, which are fast, and so-called hybrid turnstiles made from superconductors, which can be mounted in parallel to make the output current larger. Although the most accurate, a third type of pump usually made from metallic islands is too slow for making a practical current standard, but the UK researchers have now improved its performance by making it from graphene, which is a semi-metal. Graphene is a sheet of carbon just one atom thick that has a honeycomb lattice structure….
…Read more at http://physicsworld.com/cws/article/news/2013/may/28/redefining-the-ampere-with-the-help-of-graphene

New insights into what triggers lightning

What initiates a lightning strike? In the image above, multiple cloud-to-ground and cloud-to-cloud lightning strikes are observed during a night-time thunderstorm. (Courtesy: NOAA)

What initiates a lightning strike? In the image above, multiple cloud-to-ground and cloud-to-cloud lightning strikes are observed during a night-time thunderstorm. (Courtesy: NOAA)

Cosmic rays interacting with water droplets within thunderclouds could play an important role in initiating lightning strikes. That is the claim of researchers in Russia, who have studied the radio signals emitted during thousands of lightning strikes. The work could provide new insights into how and why lightning occurs in the first place.
Although most people have witnessed a flash of lightning during a thunderstorm at some point in their lives, scientists still do not completely understand what triggers the discharge in the first place. Lightning has been studied for hundreds of years, yet while many possibilities for observation are available – there are about 40 to 50 lightning strikes per second across the globe – predicting the onset of a strike is difficult…. Read more at http://physicsworld.com/cws/article/news/2013/may/07/new-insights-into-what-triggers-lightning

Paint by Particle

Satellites, balloon-borne instruments and ground-based devices make 30 million observations of the atmosphere each day. Yet these measurements still give an incomplete picture of the complex interactions within Earth’s atmosphere. Enter climate models. Through mathematical experiments, modelers can move Earth forward or backward in time to create a dynamic portrait of the planet. NASA Goddard’s Global Modeling and Assimilation Office recently ran a simulation of the atmosphere that captured how winds whip aerosols around the world. Such simulations allow scientists to better understand how these tiny particulates travel in the atmosphere and influence weather and climate. In this visualization, covering August 2006 to April 2007, watch as dust and sea salt swirl inside cyclones, carbon bursts from fires, sulfate streams from volcanoes—and see how these aerosols paint the modeled world.


NPP Launch

NASA’s National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) spacecraft was launched aboard a Delta II rocket at 5:48 a.m. EDT today, on a mission to measure both global climate changes and key weather variables.


NPP is the first step for NASA in building the next generation Earth observing satellite system. The EOS (Earth Observing System) has provided many new insights in various aspects of Earth including clouds, oceans, vegetation, glaciers and atmosphere for over a decade. Now that the system is aging, a new generation of satellites are ready to take over.

NPP is an effort led by NASA’s Goddard Space Flight Center that is carrying the first of the new sensors that will be utilized as part of that next-generation system called the Joint Polar Satellite System (JPSS). The mission will continue critical weather and climate measurements by flying advanced sensor packages. NPP will measure various properties of the Earth’s atmosphere, land surface and oceans. Its five-year mission life will help to bridge critical weather data collection before JPSS is ready for operations in 2016.