April 2011

Propagation Summary

The Solar Flux has reached the100 mark for a total of 15 days during March peaking at 110 from the 13th to the 15th. The Solar flux trend charts at Solarcycle24.com are showing a sharp rise toward the predicted peak of 130 following the dip in mid February. April will start on a high of 100 which should last for around 10 days, peaking at 115 by the 18th. The Boulder A Index has remained fairly steady during March and should remain mostly at 5 during early April. The Boulder K index should stay mainly at 2 as it has done during March. Charts can be found at www.solarcycle24.com . A 28 day forecast from NOAA is updated daily at: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml

Lyrid Meteor Shower

A Lyrid Meteor Shower is due from 19-24 April. However, any Meteor Scatter propagation will depend on where you are in the world. The best time of the year for MS DX’ing is between October and early January. More at: http://www.jt6m.org/meteor-scatter.php

Researchers Crack the Mystery of the Missing Sunspots (NASA Science News)

In 2008-2009, sunspots almost completely disappeared for two years. Solar activity dropped to hundred-year lows; Earth's upper atmosphere cooled and collapsed; the sun’s magnetic field weakened, allowing cosmic rays to penetrate the Solar System in record numbers. It was a big event, and solar physicists openly wondered, where have all the sunspots gone? Now they know. An answer has been published in the March 3rd edition of Nature. Plasma currents deep inside the sun interfered with the formation of sunspots and prolonged solar minimum," says lead author Dibyendu Nandi of the Indian Institute of Science Education and Research in Kolkata. "Our conclusions are based on a new computer model of the sun's interior." For years, solar physicists have recognized the importance of the sun's "Great Conveyor Belt." A vast system of plasma currents called ‘meridional flows’ (akin to ocean currents on Earth) travel along the sun's surface, plunge inward around the poles, and pop up again near the sun's equator. These looping currents play a key role in the 11-year solar cycle.

When sunspots begin to decay, surface currents sweep up their magnetic remains and pull them down inside the star; 300,000 km below the surface, the sun’s magnetic dynamo amplifies the decaying magnetic fields. Re-animated sunspots become buoyant and bob up to the surface like a cork in water. For the first time, Nandi’s team believes they have developed a computer model that gets the physics right for all three aspects of this process--the magnetic dynamo, the conveyor belt, and the buoyant evolution of sunspot magnetic fields. "According to our model, the trouble with sunspots actually began in back in the late 1990s during the upswing of Solar Cycle 23,"

Sunspot cycles of the last century

The thin curve shows the cyclic variation in the number of sunspots. The bars show the cumulative number of sunspot-less days. The minimum of sunspot cycle 23 was the longest in the space age. Credit: Dibyendu Nandi et al NASA Science News 2 March 2011.

Links to these articles can be found at http://www.jameswelsh.org.uk/