AGU journal highlights -- May 29, 2009

The following highlights summarize research papers that have been published in Geophysical Research Letters (GRL) or the Journal of Geophysical Research – Atmospheres (JGR-D).

In this release:

1. Avalanches of electrons may give thundercloud insights
2. Positive feedback hint between tropical cyclones and global warming
3. Moon dust stickiness depends on Sun angle
4. Probing clouds' roles in global electric circuit
5. Satellites observe Amazon basin water storage and runoff
6. Waves in Earth's radiation belt get mapped

Anyone may read the scientific abstract for any of these papers by clicking on the link provided at the end of each Highlight. You can also read the abstract by going to http://www.agu.org/pubs/search_options.shtml and inserting into the search engine the full doi (digital object identifier), e.g. 10.1029/2008JD011386. The doi is found at the end of each Highlight below.

Journalists and public information officers (PIOs) at educational or scientific institutions, who are registered with AGU, also may download papers cited in this release by clicking on the links below. Instructions for members of the news media, PIOs, and the public for downloading or ordering the full text of any research paper summarized below are available at http://www.agu.org/jinstructions.shtml .

1. Avalanches of electrons may give thundercloud insights

Understanding thundercloud electrification and lightning initiation is challenging because the ranges of electric potential and spatial extents of electric fields inside thunderclouds are not known. Directly measuring electric fields in thunderclouds is challenging—active regions of storms can cover many cubic kilometers with violent weather conditions, making it difficult to operate balloons and aircraft. Dwyer et al. hypothesize that remote sensing of thundercloud electrostatic fields can be obtained through monitoring runaway electrons, which are produced when the rate of gain of energy by electrons moving through an electric field exceeds the rate of loss of energy from ionizing the air. Such runaway electrons trigger other runaway electrons, resulting in an exponentially growing avalanche of runaway electrons moving through the storm system. The authors propose that radio frequency emissions produced by these avalanches can be monitored to map the magnitudes and directions of the electrostatic field within specific sections of a thundercloud. These radio frequencies are present only when the storm is bombarded by cosmic ray extensive air showers, allowing scientists quickly to identify particular storms that are favorable to the proposed remote sensing techniques.

Title: Remote measurements of thundercloud electrostatic fields

Authors: J. R. Dwyer and H. K. Rassoul: Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, Florida, U.S.A.;

M. A. Uman: Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida, U.S.A.

Source: Journal of Geophysical Research-Atmospheres (JGR-D) paper 10.1029/2008JD011386, 2009; http://dx.doi.org/10.1029/2008JD011386